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Java-CS003-Winter Live - HackMD
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<div id="doc" class="markdown-body container-fluid comment-enabled" data-hard-breaks="true"><h1 id="Java-CS003-Winter-Live" data-id="Java-CS003-Winter-Live"><a class="anchor hidden-xs" href="#Java-CS003-Winter-Live" title="Java-CS003-Winter-Live"><span class="octicon octicon-link"></span></a><strong><span>Java-CS003-Winter Live</span></strong></h1><h2 id="-Listings-and-Instructions" data-id="-Listings-and-Instructions"><a class="anchor hidden-xs" href="#-Listings-and-Instructions" title="-Listings-and-Instructions"><span class="octicon octicon-link"></span></a><img class="emoji" alt=":open_file_folder:" src="https://cdn.jsdelivr.net/npm/@hackmd/[email protected]/dist/images/basic/open_file_folder.png"><span> </span><em><span>Listings and Instructions</span></em></h2><ol>
<li><span>Important Words are listed by both </span><strong><span>Bold and </span><em><span>Italicized</span></em></strong><span>.</span></li>
<li><span>This is for absolute beginners having </span><strong><span>1 or more month of experience working with Java</span></strong><span>.</span></li>
<li><span>Stay tuned with us on Youtube for quality content and explanation </span><a href="https://youtube.com/channel/UCIpbqdvNWx50J79KAG1Q21A" target="_blank" rel="noopener"><strong><span>Antern</span></strong></a><span> and follow Team Antern on LinkedIn for free contents </span><a href="https://www.linkedin.com/company/team-antern" target="_blank" rel="noopener"><strong><span>LinkedIn</span></strong></a></li>
<li><span>Go through the </span><strong><span>code very carefully</span></strong><span> and</span></li>
<li><span>The Answers of </span><strong><strong><span>Test Yourself</span></strong></strong><span> is to be written in the </span><strong><span>Answers</span></strong><span class="ui-comment-inline-span"> </span><span>section on Server.</span></li>
</ol><hr><h2 id="-Topics-Covered-Here" data-id="-Topics-Covered-Here"><a class="anchor hidden-xs" href="#-Topics-Covered-Here" title="-Topics-Covered-Here"><span class="octicon octicon-link"></span></a><img class="emoji" alt=":bookmark_tabs:" src="https://cdn.jsdelivr.net/npm/@hackmd/[email protected]/dist/images/basic/bookmark_tabs.png"><span> </span><em><span>Topics Covered Here</span></em></h2><ol>
<li><strong><span>Identifiers</span></strong><br>
<span>a. </span><a href="#Sub-topic-A--Identifiers"><span>Identifiers</span></a><br>
<span>b. </span><a href="#Sub-Topic-B-Rules-of-Identifiers-or-Nomenclature"><span>Rules of Identifiers</span></a></li>
<li><strong><span>Datatypes</span></strong>
<ul>
<li><a href="#What-are-Datatypes?"><span>What are Datatypes</span></a></li>
<li><a href="#Case-Study-:-Local-Variable-Type-Inferencing"><span>Concept of Local Variable Type Inferencing.</span></a><br>
<span>a. </span><a href="#byte"><span>byte</span></a><br>
<span>b. </span><a href="#short"><span>short</span></a><br>
<span>c. </span><a href="#int"><span>int</span></a><br>
<span>d. </span><a href="#long"><span>long</span></a><br>
<span>e. </span><a href="#float"><span>float</span></a><br>
<span>f. </span><a href="#double"><span>double</span></a><br>
<span>g. </span><a href="#boolean"><span>boolean</span></a><br>
<span>h. </span><a href="#char"><span>char</span></a></li>
</ul>
</li>
<li><strong><span>Variables</span></strong>
<ul>
<li><a href="#Variables"><span>Variables.</span></a></li>
<li><a href="#Identifier-VS-Variable"><span>Identifiers vs Variables.</span></a></li>
</ul>
</li>
</ol><hr><h2 id="-Frequently-Asked-QuestionsFAQs" data-id="-Frequently-Asked-QuestionsFAQs"><a class="anchor hidden-xs" href="#-Frequently-Asked-QuestionsFAQs" title="-Frequently-Asked-QuestionsFAQs"><span class="octicon octicon-link"></span></a><img class="emoji" alt=":question:" src="https://cdn.jsdelivr.net/npm/@hackmd/[email protected]/dist/images/basic/question.png"><span> </span><strong><span>Frequently Asked Questions(FAQs)</span></strong></h2><ol>
<li><a href="#Even-when-char-and-short-have-the-same-size,-they-have-different-range."><span>Even when </span><strong><span>char</span></strong><span> and </span><strong><span>short</span></strong><span> have the same size, they have different range.</span></a></li>
<li><a href="##Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values"><span>Why using </span><strong><span>float</span></strong><span> is not preferred when dealing with higher floating point values.</span></a></li>
</ol><hr><h2 id="Topic-1-Identifiers" data-id="Topic-1-Identifiers"><a class="anchor hidden-xs" href="#Topic-1-Identifiers" title="Topic-1-Identifiers"><span class="octicon octicon-link"></span></a><em><strong><span>Topic 1: Identifiers</span></strong></em></h2><h3 id="Sub-topic-A--Identifiers" data-id="Sub-topic-A--Identifiers"><a class="anchor hidden-xs" href="#Sub-topic-A--Identifiers" title="Sub-topic-A--Identifiers"><span class="octicon octicon-link"></span></a><strong><span>Sub-topic A : Identifiers</span></strong></h3><ol>
<li>
<p><span>Definition: - </span><strong><span>Identifiers are names that are given to an element that identify an element of a program uniquely</span></strong></p>
</li>
<li>
<p><span>What can be an Idenfier in a Java Program?</span></p>
<ul>
<li><span>All constants, variables, methods, classes, interfaces, packages, interfaces, enums, etc. can be identified by assigning to them an unique name. This unique name is called Identifier.</span><br>
<img src="https://i.imgur.com/xPrupXN.jpg" alt="" loading="lazy"></li>
</ul>
</li>
<li>
<p><span>The above image </span><img class="emoji" alt=":arrow_up:" src="https://cdn.jsdelivr.net/npm/@hackmd/[email protected]/dist/images/basic/arrow_up.png"><span> is of an organism. We identify the organism as a </span><strong><span>Human</span></strong><span>. Hence </span><em><span>Human</span></em><span> is an identifier since it identifies a specific type of organism uniquely.</span></p>
</li>
<li>
<p><span>Why do we need identifiers?</span></p>
<ul>
<li><span>When it comes to real life, you must have heard about Scientific Names of organisms in Biology.</span></li>
<li><span>And you must have heard about </span><strong><span>Nomenclature</span></strong><span>, or the </span><strong><span>process of naming an organism uniquely</span></strong><span>.</span></li>
<li><span>Similarly, so as to tell our Java Virtual Machine that </span><strong><span>one element is different from another element of the same type, it is necessary to provide each element an unique name.</span></strong></li>
<li><em><strong><span>So as to avoid name-space collisions between two common elements of a program, we mainly use Identifiers.</span></strong></em></li>
<li><span>Eg: Suppose that in a class of 60 students, coincidentally 3 students having the same name namely: Krish Jaiswal. So how would you identify them uniquely? When a teacher calls “Krish Jaiswal”, all three stand up. </span><em><strong><span>Hence they all students have been allotted with Enrollment Numbers and Serial Numbers which is unique for a class. Hence the Enroll no. and Serial no. are identifiers.</span></strong></em></li>
</ul>
</li>
</ol><hr><h3 id="Sub-Topic-B-Rules-of-Identifiers-or-Nomenclature" data-id="Sub-Topic-B-Rules-of-Identifiers-or-Nomenclature"><a class="anchor hidden-xs" href="#Sub-Topic-B-Rules-of-Identifiers-or-Nomenclature" title="Sub-Topic-B-Rules-of-Identifiers-or-Nomenclature"><span class="octicon octicon-link"></span></a><strong><span>Sub-Topic B: Rules of Identifiers or Nomenclature</span></strong></h3><ol>
<li><span>Identifiers </span><strong><span>must start with</span></strong><span> </span><strong><span>$</span></strong><span> or </span><strong><span>‘_’</span></strong><span> or </span><strong><span>A-Z</span></strong><span> or </span><strong><span>a-z</span></strong><span>. It </span><strong><span>must contain</span></strong><span> any of these characters listed above.</span></li>
<li><span>An Identifier Name </span><em><strong><span>must be a legit word</span></strong></em><span>.</span><br>
<span>Eg: </span><strong><span>A person calls his/her water bottle as “Water Bottle” and not a “Bore Well”. It is possible to name the water bottle as “Bore Well” but it is not legitimate.</span></strong><span> Hence it should be a legitimate word.</span></li>
<li><em><strong><span>An Identifier can be of any length.</span></strong></em><br>
<span>Eg: If you have seen the </span><a href="https://youtu.be/bTuvEIyE6Fc" target="_blank" rel="noopener"><strong><span>Butterflow Pen Ad</span></strong></a><span>, you must have seen a person telling his name which would seem like the names of all persons living in his village. That kind of name is supported in Java but </span><strong><span>It is the Worst Programming Practice</span></strong><span>.</span></li>
<li><em><strong><span>An Identifier cannot be a Keyword or Reserved Word in Java</span></strong></em><br>
<span>Eg: -</span><pre><code class="Java hljs"> <span class="hljs-keyword">class</span> <span class="hljs-title">static</span>{ ... } <span class="hljs-comment">// Syntax Error: -</span>
<span class="hljs-built_in">int</span> <span class="hljs-keyword">yield</span> = <span class="hljs-number">10</span>; <span class="hljs-comment">//Syntax Error: -</span>
<span class="hljs-built_in">int</span> result = <span class="hljs-number">20</span>; <span class="hljs-comment">//Absolutely Correct: -</span>
</code></pre>
</li>
<li><span>There should be </span><em><strong><span>NO WHITESPACE</span></strong></em><span> character in the Identifier.</span><br>
<span>Eg: You cannot have an identifier named </span><strong><span>demo 1</span></strong><span> for an element in Java.</span></li>
<li><span>Java is </span><em><strong><span>case-sensitive</span></strong></em><span>. So if I write </span><strong><span>HELLO</span></strong><span> and </span><strong><span>hello</span></strong><span> it means a hell lot of difference.</span></li>
<li><span>The identifier </span><strong><span>must not contain a digit (0-9).</span></strong><br>
<span>Eg: Your name does not contain a digit.</span><pre><code class="Java hljs"> class <span class="hljs-number">123</span>abc{ ... } <span class="hljs-comment">//Syntax Error</span>
<span class="hljs-keyword">int</span> <span class="hljs-number">3</span>A = <span class="hljs-number">10</span>; <span class="hljs-comment">//Syntax Error</span>
<span class="hljs-keyword">int</span> A3 = <span class="hljs-number">10</span>; <span class="hljs-comment">//200% Correct.</span>
</code></pre>
</li>
</ol><h4 id="Note" data-id="Note"><a class="anchor hidden-xs" href="#Note" title="Note"><span class="octicon octicon-link"></span></a><span>Note:</span></h4><ul>
<li><span>It is not possible to remember all the rules. Generally, we just remember our </span><strong><span>Name</span></strong><span> and make out points from it.</span></li>
<li><span>Eg: </span><strong><span>Name : </span><em><span>Krish Jaiswal</span></em></strong><span> : </span><em><span>Conclusions Drawn:</span></em>
<ul>
<li><span>The Name </span><strong><span>does not begin with any Number or digit</span></strong><span>.</span></li>
<li><span>The Name </span><strong><span>may contain upper or lower case</span></strong><span> alphabetical characters.</span></li>
<li><span>Considering </span><strong><span>Krish</span></strong><span>, there is </span><strong><span>no Whitespace</span></strong><span> here.</span></li>
<li><span>Name is </span><strong><span>short and sweet</span></strong><span>. It is </span><strong><span>appropriate</span></strong><span>.</span></li>
</ul>
</li>
</ul><hr><table>
<thead>
<tr>
<th><span>Identifier Name</span></th>
<th><span>Is It Valid?</span></th>
<th><span>Invalid</span></th>
<th><span>Reason</span></th>
</tr>
</thead>
<tbody>
<tr>
<td><span>123af</span></td>
<td><s><span>Valid</span></s></td>
<td><strong><span>It is Invalid</span></strong></td>
<td><strong><span>It must not start with a Number</span></strong></td>
</tr>
<tr>
<td><span>_123</span></td>
<td><strong><span>Valid</span></strong></td>
<td><s><span>It is Invalid</span></s></td>
<td><strong><span>Valid since it begins with an underscore ( _ )</span></strong></td>
</tr>
<tr>
<td><span>$a</span></td>
<td><strong><span>Valid</span></strong></td>
<td><s><span>It is Invalid</span></s></td>
<td><strong><span>Valid since it begins with a $ symbol</span></strong></td>
</tr>
<tr>
<td><span>Abc</span></td>
<td><strong><span>Valid</span></strong></td>
<td><s><span>It is Invalid</span></s></td>
<td><strong><span>Valid since it begins with an Aplhabetical Character.</span></strong></td>
</tr>
<tr>
<td><span>1$221a</span></td>
<td><s><span>Valid</span></s></td>
<td><strong><span>It is Invalid</span></strong></td>
<td><strong><span>Invalid because an identifier cannot begin with a number.</span></strong></td>
</tr>
<tr>
<td><span>_abc</span></td>
<td><strong><span>Valid</span></strong></td>
<td><s><span>It is Invalid</span></s></td>
<td><strong><span>Valid since it begins with an underscore</span></strong></td>
</tr>
<tr>
<td><span>a bc12</span></td>
<td><s><span>Valid</span></s></td>
<td><strong><span>It is Invalid</span></strong></td>
<td><strong><span>Invalid because it contains a whitespace</span></strong></td>
</tr>
<tr>
<td><span>public</span></td>
<td><s><span>Valid</span></s></td>
<td><strong><span>It is Invalid</span></strong></td>
<td><strong><span>Invalid because it is a reserved word in Java</span></strong><span>.</span></td>
</tr>
</tbody>
</table><hr><h3 id="Sub-Topic-C-Test-Yourself" data-id="Sub-Topic-C-Test-Yourself"><a class="anchor hidden-xs" href="#Sub-Topic-C-Test-Yourself" title="Sub-Topic-C-Test-Yourself"><span class="octicon octicon-link"></span></a><strong><strong><span>Sub Topic C: Test Yourself</span></strong></strong></h3><ol>
<li><span>How many identifiers are present in the below given program.</span><br>
<span>Eg: String is an </span><strong><span>identifier</span></strong><span>. Hence </span><em><strong><span>count it only once.</span></strong></em><pre><code class="Java hljs"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Hello</span></span>{
<span class="hljs-keyword">public</span> <span class="hljs-built_in">static</span> <span class="hljs-keyword">void</span> main(<span class="hljs-keyword">String</span>[] args){
<span class="hljs-keyword">String</span> melody = <span class="hljs-string">"Why is Melody so Chocolatey"</span>;
<span class="hljs-keyword">String</span> answer = <span class="hljs-string">"Eat Melody! And that itself will give you the answer."</span>;
}
}
</code></pre>
</li>
<li><strong><span>Predict</span></strong><span> the </span><strong><span>first line</span></strong><span> where the </span><strong><span>error may originate(if any)</span></strong><span> and </span><strong><span>explain the reason</span></strong><span>. : -</span><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Demo1</span></span>{
<span class="hljs-keyword">public</span> <span class="hljs-built_in">static</span> <span class="hljs-keyword">void</span> main(<span class="hljs-keyword">String</span>[] args){
<span class="hljs-keyword">int</span> <span class="hljs-number">3</span>_ide = <span class="hljs-number">20.0</span>; <span class="hljs-comment">//1</span>
<span class="hljs-keyword">double</span> d1 = <span class="hljs-number">22</span>_00_3__<span class="hljs-number">.323</span>; <span class="hljs-comment">//2</span>
<span class="hljs-keyword">String</span> str = <span class="hljs-string">"@Auth Krish"</span>; <span class="hljs-comment">//3</span>
}
}
</code></pre>
</li>
<li><em><strong><span>Can we have a deprecated reserved word as an identifier? State the reason for the same.</span></strong></em></li>
<li><span>Which is/are a correct identifier/s?</span>
<ul class="contains-task-list">
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> ___dent</span></li>
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> _:__dent</span></li>
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> dent___</span></li>
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> _</span><em><span>$</span></em></li>
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> _transient</span></li>
<li class="task-list-item enabled"><input class="task-list-item-checkbox" type="checkbox" disabled="disabled"><span> goto</span></li>
</ul>
</li>
<li><span>Explain about </span><em><strong><span>Identifiers in your own words.</span></strong></em></li>
</ol><hr><h2 id="Conclusions" data-id="Conclusions"><a class="anchor hidden-xs" href="#Conclusions" title="Conclusions"><span class="octicon octicon-link"></span></a><strong><strong><span>Conclusions</span></strong></strong></h2><ol>
<li><span>Identifier is a name given to </span><strong><span>identify each element in a program uniquely to avoid name-space collisions.</span></strong></li>
<li><span>So as to declare a word as Identifier in your program, you </span><strong><span>need to follow the Nomenclature of Elements/Rules of using Identifiers.</span></strong></li>
<li><span>Identifiers must not be a </span><strong><span>reserved word</span></strong><span>, </span><strong><span>shouldn’t begin with a digit</span></strong><span>.</span></li>
<li><span>Using the special character </span><strong><span>$</span></strong><span> and </span><strong><span>_</span></strong><span> is allowed.</span></li>
<li><span>There must not be any </span><strong><span>WHITESPACE</span></strong><span> in the identifier.</span></li>
<li><span>Suitable Identifier </span><strong><span>must be between 3 to 10 characters long and should define the use by its name itself.</span></strong><br>
<span>Eg: </span><em><span>When writing a program that prints </span><strong><span>Hello World</span></strong><span>, the class name should be </span><strong><span>Hello</span></strong><span>.</span></em></li>
</ol><hr><hr><hr><h2 id="Topic-2-Datatypes" data-id="Topic-2-Datatypes"><a class="anchor hidden-xs" href="#Topic-2-Datatypes" title="Topic-2-Datatypes"><span class="octicon octicon-link"></span></a><em><strong><span>Topic 2: Datatypes</span></strong></em></h2><h3 id="What-are-Datatypes" data-id="What-are-Datatypes"><a class="anchor hidden-xs" href="#What-are-Datatypes" title="What-are-Datatypes"><span class="octicon octicon-link"></span></a><em><span>What are Datatypes?</span></em></h3><p><em><span>Datatypes</span></em><span>: </span><strong><span>The type of data a variable can hold is called a Datatype.</span></strong></p><ul>
<li><span>Datatypes allow variables to act as a container of a specific type which can store the values of the same specific type.</span><br>
<span>Eg: To store liquids, you will use a container or vessel. That vessel may store different volumes of water. But all those vessel will store only liquids.</span>
<ul>
<li><em><span>Hence </span><strong><span>Liquid is a type of data a vessel(variable) can hold</span></strong><span> and the volume of the vessel is the range/capacity to which the variable can hold the type of data</span></em><span>.</span><br>
<strong><span>- Vessel = Variable</span></strong><br>
<strong><span>- Volume of Vessel = Range of Datatype</span></strong><br>
<strong><span>- Liquid = Type of Data.</span></strong></li>
</ul>
</li>
</ul><p><span>Why do we need a Datatype?</span></p><ul>
<li><span>For Example: Let’s consider the same example given above. When you know the type of data, it becomes easier for you to choose a vessel. Similarly, when we consider this in Technological Terms, </span><strong><span>it becomes easier for the Compiler to choose a variable of convenient size and range.</span></strong></li>
<li><span>But in the next case, we would see that the Compiler would detect the datatype automatically and would choose the required vessel.</span></li>
<li><span>It </span><strong><span>increases the Efficiency of the Program</span></strong><span> during Runtime. It is </span><strong><span>because the Compiler knows how much memory is to be allocated for each variable of the given type.</span></strong></li>
<li><strong><span>It would make a program robust and error free by preventing any kind of incompatible type error.</span></strong></li>
</ul><h3 id="Case-Study--Local-Variable-Type-Inferencing" data-id="Case-Study--Local-Variable-Type-Inferencing"><a class="anchor hidden-xs" href="#Case-Study--Local-Variable-Type-Inferencing" title="Case-Study--Local-Variable-Type-Inferencing"><span class="octicon octicon-link"></span></a><strong><span>Case Study : Local Variable Type Inferencing</span></strong></h3><ul>
<li>
<p><span>An Interesting thing is to know that with JDK 10, you can use variables without even using datatypes.</span></p>
</li>
<li>
<p><span>We will very soon learn that </span><strong><span>So as to use variables, we </span><em><strong><span>Must declare the variable prior to its use and it must be initialized with a value and its initializer type.</span></strong></em></strong></p>
</li>
<li>
<p><span>But, in this case, the Compiler would automatically detect the type of initializer.</span></p>
</li>
<li>
<p><span>This reduces code redundancy and helps in situations where deciding the type is difficult to make out or cannot be denoted.</span></p>
</li>
<li>
<p><em><span>Definition</span></em><span>: </span><strong><span>Local Variable Type Inferencing is a concept where the Compiler automatically identifies/recognizes the type of data that is to be stored in the variables.</span></strong></p>
</li>
<li>
<p><span>It is achieved by using a </span><strong><span>context-specific identifier</span></strong><span> namely: </span><strong><span>var</span></strong><span>.</span></p>
</li>
<li>
<p><strong><span>var</span></strong><span> is context-specific since it depends on the place of the usage in a Java Program.</span></p>
</li>
<li>
<p><span>Eg: Let’s Consider the Given Example: -</span></p>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Foo</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-keyword">var</span> i = <span class="hljs-number">10</span>; <span class="hljs-comment">//var is an context specific identifier here.</span>
<span class="hljs-built_in">int</span> <span class="hljs-keyword">var</span> = <span class="hljs-number">10</span>; <span class="hljs-comment">//var is an context-indefinite/user-defined identifier here.</span>
}
}
</code></pre>
</li>
<li>
<p><img src="https://i.imgur.com/J4ChVbq.png" alt="" loading="lazy"></p>
</li>
<li>
<p><span>In the above picture, </span><img class="emoji" alt=":arrow_up:" src="https://cdn.jsdelivr.net/npm/@hackmd/[email protected]/dist/images/basic/arrow_up.png"><span> its visible that </span><strong><span>var</span></strong><span> acts as a </span><strong><span>context-specific identifier</span></strong><span>.</span></p>
</li>
<li>
<p><strong><span>Definition</span></strong><span>: </span><strong><span>Context-Specific Identifier means an identifier(not a reserved word) having different functionalities when used at different places in a Java program.</span></strong></p>
</li>
<li>
<p><span>Eg: of a program where </span><strong><span>var</span></strong><span> is an user-defined identifier.</span></p>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo2</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">int</span> <span class="hljs-keyword">var</span>[] = {<span class="hljs-number">1</span>,<span class="hljs-number">23</span>,<span class="hljs-number">34</span>,<span class="hljs-number">2</span>,<span class="hljs-number">2</span>,<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>}; <span class="hljs-comment">//Here var is an user defined identifier.</span>
}
}
</code></pre>
</li>
<li>
<p><span>This Program shown above would not show any error.</span></p>
</li>
<li>
<p><span>Syntax of User-Defined </span><strong><span>var</span></strong><span> named Identifier.</span></p>
</li>
<li>
<p><img src="https://i.imgur.com/V7HW1JE.png" alt="" loading="lazy"></p>
</li>
<li>
<p><span>We would learn more about Local Variable Type Inferencing very soon in another Notes.</span></p>
</li>
</ul><hr><h3 id="Is-Java-Statically-Typed-Language" data-id="Is-Java-Statically-Typed-Language"><a class="anchor hidden-xs" href="#Is-Java-Statically-Typed-Language" title="Is-Java-Statically-Typed-Language"><span class="octicon octicon-link"></span></a><strong><span>Is Java Statically Typed Language?</span></strong></h3><ol>
<li>
<p><span>The Answer is </span><em><strong><span>Yes</span></strong></em><span>.</span></p>
</li>
<li>
<p><strong><span>Reasons: -</span></strong></p>
<ul>
<li><strong><span>A variable must be declared with a datatype before its use.</span></strong></li>
<li><strong><span>It must be initialized with an </span><em><span>initializer</span></em><span> before use</span></strong><span>.</span></li>
</ul>
</li>
<li>
<p><strong><span>Definition: Statically Typed Language is a Programming Language in which the Programmer needs to specify the type of data a variable can hold </span><em><span>EXPLICITLY</span></em><span> so that the Compiler can detect the common type errors long before the program actually executes</span></strong><span>.</span></p>
</li>
</ol><hr><h3 id="Question-Do-you-think-that-Java-is-still-statically-typed-after-the-introduction-of-Local-Variable-Type-Inferencing-in-JDK-10" data-id="Question-Do-you-think-that-Java-is-still-statically-typed-after-the-introduction-of-Local-Variable-Type-Inferencing-in-JDK-10"><a class="anchor hidden-xs" href="#Question-Do-you-think-that-Java-is-still-statically-typed-after-the-introduction-of-Local-Variable-Type-Inferencing-in-JDK-10" title="Question-Do-you-think-that-Java-is-still-statically-typed-after-the-introduction-of-Local-Variable-Type-Inferencing-in-JDK-10"><span class="octicon octicon-link"></span></a><strong><span>Question: Do you think that Java is still statically typed after the introduction of Local Variable Type Inferencing in JDK 10.?</span></strong></h3><hr><h2 id="Fooling-around-with-Java-Datatypes" data-id="Fooling-around-with-Java-Datatypes"><a class="anchor hidden-xs" href="#Fooling-around-with-Java-Datatypes" title="Fooling-around-with-Java-Datatypes"><span class="octicon octicon-link"></span></a><strong><span>Fooling around with Java Datatypes</span></strong><span>.</span></h2><ol>
<li>
<p><a href="https://s4.aconvert.com/convert/p3r68-cdx67/ae6mw-m0yl6.svg" target="_blank" rel="noopener"><strong><span>View the Type Dissociation into Primitive and Non-Primitive</span></strong></a></p>
</li>
<li>
<p><span>In the image shown above, it is clear that there are two forms of Datatypes namely: </span><strong><span>Primitive and Non-Primitive</span></strong><span>.</span></p>
</li>
</ol><h4 id="Primitive-Datatypes" data-id="Primitive-Datatypes"><a class="anchor hidden-xs" href="#Primitive-Datatypes" title="Primitive-Datatypes"><span class="octicon octicon-link"></span></a><em><strong><span>Primitive Datatypes</span></strong></em></h4><ul>
<li><strong><span>Signed Numbers --> Signed Numbers are numbers whose range is from a negative to a positive number and these numbers contain the Most Significant Bit which denotes whether the number is negative or positive.</span></strong></li>
<li><strong><span>Datatypes having a fixed range and a predefined size built for just improving the efficiency of the program that cannot be instantiated, are called Primitive Datatypes.</span></strong></li>
<li><span>But what is </span><strong><span>Instantiation</span></strong><span>?</span></li>
<li><strong><span>Instantiation means creating the objects so that its properties(variables) like hair color, skin color, etc. and behavior(methods) like eating, sleeping, etc. can be accessed.</span></strong><span> We will learn more about Instantiation in the subsequent notes of Object Oriented Programming.</span></li>
<li><span>There are some </span><strong><span>special characteristics</span></strong><span> of these types: -</span>
<ul>
<li><strong><span>They have a fixed size.</span></strong><br>
<span>Eg: </span><a href="https://www.middleschoolchemistry.com/img/content/lessons/3.2/girl_examining_cylinder_in_graduated_cylinder.jpg" target="_blank" rel="noopener"><strong><span>Visit this Link</span></strong></a><span> You have measuring cylinders which consumes some area when placed on a table.</span></li>
<li><strong><span>They have a fixed range.</span></strong><br>
<span>Eg: For a measuring cylinder, they can store only a fixed volume. If we try to fill more, an overflow happens. In Java, overflow of range in case of Primitive types results in a syntax error namely </span><strong><span>integer number too large</span></strong><span>.</span></li>
<li><strong><span>They store a specific datatype</span></strong><br>
<span>Eg: You store water in an overhead tank and not fruit juice. In case of Java, if there is a type mismatch, then a syntax error namely </span><strong><span>incompatible types</span></strong><span>.</span></li>
<li><strong><span>You cannot create the object of Primitive types</span></strong><br>
<span>EG:</span></li>
</ul>
<pre><code class="Java hljs"> <span class="hljs-built_in">int</span> a = <span class="hljs-keyword">new</span> <span class="hljs-built_in">int</span>(<span class="hljs-number">20</span>); <span class="hljs-comment">//Results in an error.</span>
<span class="hljs-built_in">int</span> a = <span class="hljs-number">20</span>; <span class="hljs-comment">//Works Successfully</span>
</code></pre>
</li>
<li><span>Its important to see the division of Java Datatypes in the Primitive and Non-Primitive Hierarchy. If you not yet seen it, its important to see it…</span></li>
</ul><h5 id="Why-there-are-Primitive-types-at-all-in-Java" data-id="Why-there-are-Primitive-types-at-all-in-Java"><a class="anchor hidden-xs" href="#Why-there-are-Primitive-types-at-all-in-Java" title="Why-there-are-Primitive-types-at-all-in-Java"><span class="octicon octicon-link"></span></a><strong><span>Why there are Primitive types at all in Java?</span></strong></h5><ol>
<li><span>Answer to this, it is just for increasing the efficiency of a Java Program both by Memory and Time.</span></li>
<li><span>As already mentioned, its easier for you to choose a vessel prior to filling up the liquid in the vessel.</span></li>
<li><span>Now watch this dramatic conversation between a Compiler and a Programmer on the program given below.</span></li>
</ol><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo3</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String args[]</span>)</span>{
<span class="hljs-built_in">int</span> a = <span class="hljs-number">20</span>;
<span class="hljs-built_in">double</span> b = <span class="hljs-number">90.4543</span>;
<span class="hljs-built_in">char</span> ch = <span class="hljs-string">'a'</span>;
}
}
</code></pre><p><strong><span>Programmer</span></strong><span>: Hey </span><em><span>Compiler</span></em><span>, please </span><strong><span>compile</span></strong><span> this source code and create a bytecode file.</span><br>
<strong><span>Compiler</span></strong><span>: Okay dude, there are no syntax errors and everything seems fine. I am compiling the code…Please wait a moment.</span><br>
<strong><span>Compiler</span></strong><span>: Hey Pal, I have compiled the code and have mentioned </span><strong><span>how many bytes of memory should be allocated for the Primitive types you initialized in the ByteCode</span></strong><span>.(</span><em><span>Bytecode or intermediate code is the highly optimized, platform independent set of instructions that is passed to the JVM to be converted to Machine Native Code.</span></em><span>)</span><br>
<strong><span>Programmer</span></strong><span>: Why do you need to tell the JVM that how much size is to be required?</span><br>
<strong><span>Compiler</span></strong><span>: It is necessary Pal. If I dont inform JVM about the size, it would have to search it by himself and that would take a lot of time.</span><br>
<strong><span>Compiler</span></strong><span>: Moreover, I cannot let you and JVM struggle for time and space.</span><br>
<strong><span>Programmer</span></strong><span>: Greatful to you, my friend.</span></p><ol start="4">
<li><span>So, this is the dramatic reason why Primitive types have a fixed range and size.</span></li>
</ol><hr><p><span>Time to know about the Primitive Datatypes one by one.</span></p><h1 id="Integral-Datatypes" data-id="Integral-Datatypes"><a class="anchor hidden-xs" href="#Integral-Datatypes" title="Integral-Datatypes"><span class="octicon octicon-link"></span></a><strong><span>Integral Datatypes</span></strong></h1><h2 id="byte" data-id="byte"><a class="anchor hidden-xs" href="#byte" title="byte"><span class="octicon octicon-link"></span></a><strong><span>byte</span></strong></h2><ol>
<li><strong><span>Size --> 1 Byte or 8 bits.</span></strong></li>
<li><strong><span>Range --> -128 to 127.</span></strong></li>
<li><span>Generally used in case of </span><strong><span>transferring Strings across Networks and writing files with Character and Byte Streams</span></strong><span>.</span></li>
<li><strong><span>MAX_VALUE : 127</span></strong></li>
<li><strong><span>MIN_VALUE : -128</span></strong></li>
<li><img src="https://i.imgur.com/C2lfz1T.jpg" alt="" loading="lazy"></li>
<li><span>The </span><strong><span>MSD</span></strong><span> stands for </span><strong><span>Most Significant Bit</span></strong><span>. This stores either 0(negative) or 1(positive). </span><strong><span>In Signed Integers, this MSD signifies whether the number stored is positive(zero or more than zero) or negative(less than zero).</span></strong></li>
<li><span>If you add </span><strong><span>2^6 + 2^5 + 2^4 + 2^3 + 2^2 + 2^1 + 2^0</span></strong><span>, you would get the sum as </span><strong><span>127</span></strong><span>.</span></li>
</ol><h3 id="Operations-on-a-byte-datatype" data-id="Operations-on-a-byte-datatype"><a class="anchor hidden-xs" href="#Operations-on-a-byte-datatype" title="Operations-on-a-byte-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on a </span><em><span>byte</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo4</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">double</span> a = <span class="hljs-number">20.52</span>;
<span class="hljs-built_in">byte</span> b = a; <span class="hljs-comment">//Possible Loss of Precision.</span>
}
}
</code></pre>
</li>
<li>
<pre><code class="Java hljs">
<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo5</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
String str = <span class="hljs-string">"Krish Jaiswal"</span>;
<span class="hljs-built_in">byte</span> b = str; <span class="hljs-comment">// Incompatible Types. found: java.lang.String ; required: byte</span>
}
}
</code></pre>
<strong><span>Infamous Error in case of Datatypes are :-</span></strong>
<ol>
<li><strong><span>Possible Loss of Precision</span></strong><span>: It is caused due </span><em><strong><span>to possible loss of some value during assignment to a variable having a different type</span></strong></em><span>.</span></li>
<li><strong><span>Incompatible Types</span></strong><span>: It is caused when two datatypes, which are </span><em><strong><span>not compatible and hold no relation with each other are assigned or explicitly casted.</span></strong></em></li>
</ol>
</li>
</ol><hr><h2 id="short" data-id="short"><a class="anchor hidden-xs" href="#short" title="short"><span class="octicon octicon-link"></span></a><strong><span>short</span></strong></h2><ol>
<li><strong><span>Size --> 2 Byte or 16 bits.</span></strong></li>
<li><strong><span>Range --> -32768 to 32767.</span></strong></li>
<li><span>Was </span><strong><span>previously used for Intel 8086 16 bit Processors which existed during late 1990s and early 2000s since it provided efficiency there too.</span></strong></li>
<li><strong><span>MAX_VALUE : 32767</span></strong></li>
<li><strong><span>MIN_VALUE : -32768</span></strong></li>
<li><span>The </span><strong><span>MSD</span></strong><span> stands for </span><strong><span>Most Significant Bit</span></strong><span>. This stores either 0(negative) or 1(positive). </span><strong><span>In Signed Integers, this MSD signifies whether the number stored is positive(zero or more than zero) or negative(less than zero).</span></strong></li>
<li><span>If you add </span><strong><span>2^15 + 2^14 + 2^13 + 2^12 + 2^11 + 2^10 + 2^9</span></strong><span> + …, you would get the sum as </span><strong><span>32767</span></strong><span>.</span></li>
</ol><h3 id="Operations-on-a-short-datatype" data-id="Operations-on-a-short-datatype"><a class="anchor hidden-xs" href="#Operations-on-a-short-datatype" title="Operations-on-a-short-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on a </span><em><span>short</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo6</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">double</span> a = <span class="hljs-number">20.52</span>;
<span class="hljs-built_in">short</span> b = a; <span class="hljs-comment">//Possible Loss of Precision.</span>
}
}
</code></pre>
</li>
<li>
<pre><code class="Java hljs">
<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo7</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
String str = <span class="hljs-string">"Krish Jaiswal"</span>;
<span class="hljs-built_in">short</span> b = str; <span class="hljs-comment">// Incompatible Types. found: java.lang.String ; required: short</span>
}
}
</code></pre>
</li>
</ol><hr><h2 id="int" data-id="int"><a class="anchor hidden-xs" href="#int" title="int"><span class="octicon octicon-link"></span></a><strong><span>int</span></strong></h2><ol>
<li><strong><span>Size --> 4 Bytes or 32 bits.</span></strong></li>
<li><strong><span>Range --> -2147483648 to 2147483647.</span></strong></li>
<li><span>It is the </span><strong><span>default integral datatype. It is frequently used. It has a wide range of uses.</span></strong></li>
<li><strong><span>MAX_VALUE : 2147483647</span></strong></li>
<li><strong><span>MIN_VALUE : -2147483648</span></strong></li>
<li><span>If you add </span><strong><span>2^31 + 2^30 + 2^29 + 2^28 + 2^27 + 2^26 + 2^25</span></strong><span> + …, you would get the sum as </span><strong><span>2147483647</span></strong><span>.</span></li>
</ol><h3 id="Operations-on-a-int-datatype" data-id="Operations-on-a-int-datatype"><a class="anchor hidden-xs" href="#Operations-on-a-int-datatype" title="Operations-on-a-int-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on a </span><em><span>int</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo8</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">int</span> b = <span class="hljs-number">10l</span>; <span class="hljs-comment">//Possible Loss of Precision since "l" denotes a long datatype.</span>
}
}
</code></pre>
</li>
<li>
<pre><code class="Java hljs">
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Demo9</span></span>{
<span class="hljs-keyword">public</span> <span class="hljs-built_in">static</span> <span class="hljs-keyword">void</span> main(<span class="hljs-keyword">String</span>[] args){
<span class="hljs-keyword">String</span> str = <span class="hljs-string">"Krish Jaiswal"</span>;
<span class="hljs-keyword">int</span> b = str; <span class="hljs-comment">// Incompatible Types. found: java.lang.String ; required: int</span>
}
}
</code></pre>
</li>
<li>
<pre><code class="Java hljs">
<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo10</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">int</span> a = <span class="hljs-number">20</span>;
<span class="hljs-built_in">int</span> b = a*<span class="hljs-number">4</span>+<span class="hljs-number">1</span>;
System.<span class="hljs-keyword">out</span>.println(b);
}
}
</code></pre>
</li>
</ol><h2 id="long" data-id="long"><a class="anchor hidden-xs" href="#long" title="long"><span class="octicon octicon-link"></span></a><strong><span>long</span></strong></h2><ol>
<li><strong><span>Size --> 8 Bytes or 64 bits.</span></strong></li>
<li><strong><span>Range --> -9_223_372_036_854_775_808 to 9_223_372_036_854_775_807.</span></strong></li>
<li><span>It is a signed 64 bit type used for storing excessive large or small numbers that may surpass the range of </span><strong><span>int</span></strong><span> datatype.</span></li>
<li><strong><span>MAX_VALUE : 9_223_372_036_854_775_807</span></strong></li>
<li><strong><span>MIN_VALUE : -9_223_372_036_854_775_808</span></strong></li>
<li><span>If you add </span><strong><span>2^63 + 2^62 + 2^61 + 2^60 + 2^59 + 2^58 + 2^57</span></strong><span> + …, you would get the sum as </span><strong><span>9_223_372_036_854_775_807</span></strong><span>.</span></li>
</ol><h3 id="Operations-on-long-datatype" data-id="Operations-on-long-datatype"><a class="anchor hidden-xs" href="#Operations-on-long-datatype" title="Operations-on-long-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on </span><em><span>long</span></em><span> datatype.</span></strong></h3><ol>
<li>
<pre><code class="Java hljs">
<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo11</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
String str = <span class="hljs-string">"Krish Jaiswal"</span>;
<span class="hljs-built_in">long</span> b = str; <span class="hljs-comment">// Incompatible Types. found: java.lang.String ; required: int</span>
}
}
</code></pre>
</li>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo12</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">long</span> var1 = <span class="hljs-number">104</span> * <span class="hljs-number">203</span> ;
<span class="hljs-built_in">long</span> var2 = <span class="hljs-number">2147483648</span> ; <span class="hljs-comment">//Gives a compile time error: integer number too large.</span>
<span class="hljs-comment">/*
* A long datatype has a default value as 0l.
* Here 'l' denotes that the number is of long type.
* Since all numbers are by default of 'int' type, Compiler gives an error if it finds that the range is exceeded.
*/</span>
<span class="hljs-built_in">long</span> var3 = <span class="hljs-number">2147483648l</span> ; <span class="hljs-comment">// No Error.</span>
}
}
</code></pre>
</li>
</ol><hr><h1 id="Floating-Point-Types" data-id="Floating-Point-Types"><a class="anchor hidden-xs" href="#Floating-Point-Types" title="Floating-Point-Types"><span class="octicon octicon-link"></span></a><strong><span>Floating-Point Types</span></strong></h1><ol>
<li><span>Java implements the standards of IEEE 754 set of floating point types and operators.</span></li>
<li><span>Floating Point means </span><strong><span>real numbers</span></strong><span>.</span><br>
<span>Eg: There are 2 consecutive numbers. Let’s say 20 and 21. So the number between 20 and 21 can be 20.302, 20.1, 20.2, etc.</span></li>
</ol><h2 id="float" data-id="float"><a class="anchor hidden-xs" href="#float" title="float"><span class="octicon octicon-link"></span></a><strong><span>float</span></strong></h2><ol>
<li><strong><span>Size --> 4 Bytes or 32 bits.</span></strong></li>
<li><strong><span>Range --> 1.4e-045 to 3.4e+38.</span></strong></li>
<li><span>It specifies a </span><em><span>single-precision</span></em><span> value that uses 32 bits of storage. Single precision are useful on some processors and hence is used in storing floating point values.</span></li>
</ol><h3 id="Operations-on-float-datatype" data-id="Operations-on-float-datatype"><a class="anchor hidden-xs" href="#Operations-on-float-datatype" title="Operations-on-float-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on </span><em><span>float</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo13</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">float</span> f = <span class="hljs-number">2.13421f</span>;
<span class="hljs-comment">/*
* Since all the floating point numbers have 'double' type as default type, we need to explicitly specify that our number is a float type.
* This is done by adding 'f' to the number.
*/</span>
<span class="hljs-built_in">float</span> f2 = <span class="hljs-number">32.3212123</span> ; <span class="hljs-comment">//Compile Time Error occurs: Possible Loss of Precision.</span>
}
}
</code></pre>
</li>
</ol><h2 id="double" data-id="double"><a class="anchor hidden-xs" href="#double" title="double"><span class="octicon octicon-link"></span></a><strong><span>double</span></strong></h2><ol>
<li><strong><span>Size --> 8 Bytes or 64 bits.</span></strong></li>
<li><strong><span>Range --> 4.9e-324 to 1.8e+308 .</span></strong></li>
<li><span>It specifies a Double Precision that uses 64 bit of storage. It is the default datatype for all floating datatypes.</span></li>
</ol><h3 id="Operations-on-double-datatype" data-id="Operations-on-double-datatype"><a class="anchor hidden-xs" href="#Operations-on-double-datatype" title="Operations-on-double-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on </span><em><span>double</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo14</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">double</span> d = <span class="hljs-number">2.48213121</span>;
}
}
</code></pre>
</li>
</ol><hr><h1 id="Character" data-id="Character"><a class="anchor hidden-xs" href="#Character" title="Character"><span class="octicon octicon-link"></span></a><strong><span>Character</span></strong></h1><h2 id="char" data-id="char"><a class="anchor hidden-xs" href="#char" title="char"><span class="octicon octicon-link"></span></a><strong><span>char</span></strong></h2><ol>
<li><span>This datatype is </span><strong><span>used to store characters.</span></strong></li>
<li><span>It uses </span><strong><span>Unicode standard that is a fully international character set of 2^16 characters containing Arabic, Chinese, Hebrew, etc. totalling to 65,535 characters.</span></strong></li>
<li><span>It is </span><strong><span>not a signed datatype. It means that it cannot have a negative value</span></strong><span>.</span></li>
<li><span>Unicode system is combination of other smaller character sets like </span><strong><span>ISO-Latin1</span></strong><span> and </span><strong><span>ASCII.</span></strong></li>
<li><span>Characters are </span><strong><span>internally represented as integral numbers.</span></strong><br>
<span>Eg: Try executing this code:-</span><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Demo15</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">char</span> ch = <span class="hljs-string">'a'</span>;
<span class="hljs-built_in">int</span> asc = ch; <span class="hljs-comment">//Compiler internally represents a character as an integer number and hence assigning a character to an integer type variable gives no errors at all.</span>
System.<span class="hljs-keyword">out</span>.println(<span class="hljs-string">"Integer Value of "</span>+ch+<span class="hljs-string">" is : "</span>+asc);
}
}
</code></pre>
<span>Output: -</span><pre><code> Integer Value of a is : 97
</code></pre>
</li>
<li><span>We would be understanding </span><strong><span>Implicit Type Casting</span></strong><span> in some other lectures.</span></li>
</ol><h1 id="Boolean" data-id="Boolean"><a class="anchor hidden-xs" href="#Boolean" title="Boolean"><span class="octicon octicon-link"></span></a><strong><span>Boolean</span></strong></h1><h2 id="boolean" data-id="boolean"><a class="anchor hidden-xs" href="#boolean" title="boolean"><span class="octicon octicon-link"></span></a><strong><span>boolean</span></strong></h2><ol>
<li><span>Does your toothpaste have salt in it?</span></li>
<li><span>Are you 54 years old?</span></li>
<li><em><span>boolean</span></em><span> is a datatype which helps us to </span><strong><span>classify a condition in </span><em><strong><span>true</span></strong></em><span> and </span><em><strong><span>false</span></strong></em></strong><span> .</span></li>
<li><span>So, imagine this situation:-</span>
<ul>
<li><span>Person 1: Is it sunny Outside?</span></li>
<li><span>Person 2: No (false).</span></li>
<li><span>Person 2: Should we carry umbrella?</span></li>
<li><span>Person 1: No (false).</span></li>
</ul>
</li>
<li><span>These things are represented by </span><strong><span>boolean</span></strong><span> datatype.</span></li>
<li><span>All </span><strong><span>Relational and Logical conditions are either in true or in false, which means they have </span><strong><span>boolean</span></strong><span> as the only type.</span></strong></li>
<li><span>Interestingly, it </span><strong><span>cannot be type casted (either implicitly or explicitly) to any other datatype.</span></strong><span> Doing that would give a Compile Time Error : </span><strong><span>incompatible types</span></strong><span>.</span></li>
</ol><h3 id="Operations-on-boolean-datatype" data-id="Operations-on-boolean-datatype"><a class="anchor hidden-xs" href="#Operations-on-boolean-datatype" title="Operations-on-boolean-datatype"><span class="octicon octicon-link"></span></a><strong><span>Operations on </span><em><span>boolean</span></em><span> datatype</span></strong></h3><ol>
<li>
<pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Demo16</span></span>{
<span class="hljs-keyword">public</span> <span class="hljs-built_in">static</span> <span class="hljs-keyword">void</span> main(<span class="hljs-keyword">String</span>[] args){
<span class="hljs-keyword">boolean</span> b = <span class="hljs-literal">true</span>;
<span class="hljs-keyword">boolean</span> x = <span class="hljs-literal">false</span>;
<span class="hljs-keyword">int</span> a = <span class="hljs-number">20</span>;
<span class="hljs-keyword">boolean</span> result = (a><span class="hljs-number">20</span>)?<span class="hljs-literal">true</span>:<span class="hljs-literal">false</span>; <span class="hljs-comment">//Ternary Operations would be covered in subsequent lectures.</span>
<span class="hljs-keyword">int</span> val = <span class="hljs-number">1</span>;
<span class="hljs-keyword">boolean</span> wrong = val; <span class="hljs-comment">//Compile Time Error. Incompatible types.</span>
}
}
</code></pre>
</li>
</ol><hr><h1 id="How-Prepared-you-Are" data-id="How-Prepared-you-Are"><a class="anchor hidden-xs" href="#How-Prepared-you-Are" title="How-Prepared-you-Are"><span class="octicon octicon-link"></span></a><strong><span>How Prepared you Are?</span></strong></h1><ol>
<li><span>What would be the first line to generate an error in this program.: -</span><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Test2</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">int</span> a = <span class="hljs-number">10.34</span>; <span class="hljs-comment">// 1</span>
<span class="hljs-built_in">double</span> b = <span class="hljs-number">45.302f</span>; <span class="hljs-comment">//2</span>
<span class="hljs-built_in">char</span> ch = <span class="hljs-number">97</span>; <span class="hljs-comment">//3;</span>
}
}
</code></pre>
</li>
<li><span>Why Java makes use of primitive datatypes?</span></li>
<li><span>Predict the Output:-</span><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Test3</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">int</span> g = <span class="hljs-string">'a'</span>;
System.<span class="hljs-keyword">out</span>.println(g);
}
}
</code></pre>
</li>
<li><span>Predict the Output: -</span><pre><code class="Java hljs"> <span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title">Test4</span>{
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(<span class="hljs-params">String[] args</span>)</span>{
<span class="hljs-built_in">double</span> <span class="hljs-number">2f</span>t = <span class="hljs-number">50.32f</span>;
}
}
</code></pre>
</li>
</ol><hr><h1 id="Variables" data-id="Variables"><a class="anchor hidden-xs" href="#Variables" title="Variables"><span class="octicon octicon-link"></span></a><strong><span>Variables</span></strong></h1><ol>
<li><strong><span>Definition: Variables are just like vessels which store some specific thing. In tech terms, Variables are </span><em><span>user-allocated memory locations</span></em><span> which store some value and their value can be changed during the execution of a program</span></strong><span>.</span></li>
<li><strong><span>user-allocated</span></strong><span> since user tells the compiler to reserve the memory location for a vessel of </span><em><span>x</span></em><span> type.</span></li>
<li><span>All variables are identifiers so they follow all the naming conventions of identifiers.</span></li>
</ol><h2 id="Identifier-VS-Variable" data-id="Identifier-VS-Variable"><a class="anchor hidden-xs" href="#Identifier-VS-Variable" title="Identifier-VS-Variable"><span class="octicon octicon-link"></span></a><strong><span>Identifier VS Variable</span></strong></h2><table>
<thead>
<tr>
<th><span>Identifier</span></th>
<th><span>Variable</span></th>
</tr>
</thead>
<tbody>
<tr>
<td><span>Identifier is a unique name given to each and every entity of a program for its unique identification in the whole program.</span></td>
<td><span>Variables are user allocated memory locations that hold some value which can be changed during the execution of the program.</span></td>
</tr>
<tr>
<td><span>They are used for identification purposes.</span></td>
<td><span>They are used for storing values of a given type</span></td>
</tr>
</tbody>
</table><hr><h1 id="Frequently-Asked-Questions" data-id="Frequently-Asked-Questions"><a class="anchor hidden-xs" href="#Frequently-Asked-Questions" title="Frequently-Asked-Questions"><span class="octicon octicon-link"></span></a><strong><span>Frequently Asked Questions</span></strong></h1><h2 id="Even-when-char-and-short-have-the-same-size-they-have-different-range" data-id="Even-when-char-and-short-have-the-same-size-they-have-different-range"><a class="anchor hidden-xs" href="#Even-when-char-and-short-have-the-same-size-they-have-different-range" title="Even-when-char-and-short-have-the-same-size-they-have-different-range"><span class="octicon octicon-link"></span></a><em><strong><span>Even when char and short have the same size, they have different range.</span></strong></em></h2><p><span>Answer: </span><em><span>char</span></em><span> is not a integer or floating point datatype. It means that it cannot have any negative value. Hence the Most Significant Bit would be free since it need not store any 0 or 1 for denoting a positive or negative number.But </span><em><span>short</span></em><span> is a integral datatype used for storing integers. So, the Compiler should be made aware that the number stored in a variable of type </span><em><span>short</span></em><span> is positive or negative. Hence the Most Significant Bit stores 0 or 1 denoting the number as positive or negative. Hence, </span><strong><span>char being of 2 bytes has a max range of 65,535 and short being of 2 bytes has a max range of 32767</span></strong></p><hr><h2 id="Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values" data-id="Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values"><a class="anchor hidden-xs" href="#Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values" title="Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values"><span class="octicon octicon-link"></span></a><em><strong><span>Why using float is not preferred when dealing with higher floating point values.</span></strong></em></h2><p><span>Answer: </span><em><span>float</span></em><span> results in loss of precision at higher values. Hence it is not safe to use float with higher floating point values.</span></p></div>
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<li><a href="#Java-CS003-Winter-Live" title="Java-CS003-Winter Live">Java-CS003-Winter Live</a><ul class="nav">
<li><a href="#-Listings-and-Instructions" title=" Listings and Instructions"> Listings and Instructions</a></li>
<li><a href="#-Topics-Covered-Here" title=" Topics Covered Here"> Topics Covered Here</a></li>
<li><a href="#-Frequently-Asked-QuestionsFAQs" title=" Frequently Asked Questions(FAQs)"> Frequently Asked Questions(FAQs)</a></li>
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<li><a href="#Sub-topic-A--Identifiers" title="Sub-topic A : Identifiers">Sub-topic A : Identifiers</a></li>
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<li><a href="#What-are-Datatypes" title="What are Datatypes?">What are Datatypes?</a></li>
<li><a href="#Case-Study--Local-Variable-Type-Inferencing" title="Case Study : Local Variable Type Inferencing">Case Study : Local Variable Type Inferencing</a></li>
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<li><a href="#Even-when-char-and-short-have-the-same-size-they-have-different-range" title="Even when char and short have the same size, they have different range.">Even when char and short have the same size, they have different range.</a></li>
<li><a href="#Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values" title="Why using float is not preferred when dealing with higher floating point values.">Why using float is not preferred when dealing with higher floating point values.</a></li>
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<li><a href="#Case-Study--Local-Variable-Type-Inferencing" title="Case Study : Local Variable Type Inferencing">Case Study : Local Variable Type Inferencing</a></li>
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<li><a href="#Why-using-float-is-not-preferred-when-dealing-with-higher-floating-point-values" title="Why using float is not preferred when dealing with higher floating point values.">Why using float is not preferred when dealing with higher floating point values.</a></li>
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