Acquiring Tokens with username and password

ADAL4J supports in the user name and password flow for public client applications. In general Microsoft does not advice customers to use it as it's less secure than the other flows, and it is not compatible with conditional access (because if the resource requires conditional access, the call to acquire token will just fail, given that this is not an interactive flow (the STS does not have an opportunity to present a dialog to the user to tell him/her that s/he needs to do multiple factor authentication). The preferred flow for acquiring a token silently on Windows domain joined machines is Integrated Windows Authentication. Otherwise you can also use Device code flow

Although this is useful in some cases (DevOps scenarios), if you want to use Username/password in interactive scenarios where you provide your own UI, you should really think about how to move away from it. By using username/password you are giving-up a number of things:

• core tenants of modern identity: password gets fished, replayed. Because we have this concept of a share secret that can be intercepted. This is incompatible with passwordless.
• users who need to do MFA won't be able to sign-in (as there is no interaction)
• Users won't be able to do single sign-on

      final String AUTHORITY;
      final String APP_ID;
      String userName;
      String password;
      List<String> scopes;

       PublicClientApplication pca = new PublicClientApplication.Builder(APP_ID).
                authority(AUTHORITY).
                build();

       UserNamePasswordParameters paramaters = 
                        UserNamePasswordParameters.builder(
                            scopes,
                            userName,
                            password.toCharArray()).build();

        IAuthenticationResult result = pca.acquireToken(parameters).get();

For more information about why you want to avoid using this grant, you can, for instance read the following article which explains why Microsoft is working to make passwords a thing of the past.

To view a sample of authenticating via the username-password flow, take a look at Java console application sample.