diff --git a/src/one/nio/mem/MappedFile.java b/src/one/nio/mem/MappedFile.java
index 553e0fcf..1c3328b6 100755
--- a/src/one/nio/mem/MappedFile.java
+++ b/src/one/nio/mem/MappedFile.java
@@ -160,9 +160,17 @@ public static long map(RandomAccessFile f, int mode, long start, long size) thro
         }
 
         try {
-            Method map0 = Class.forName("sun.nio.ch.FileChannelImpl").getDeclaredMethod("map0", int.class, long.class, long.class);
-            map0.setAccessible(true);
-            return (Long) map0.invoke(f.getChannel(), mode, start, size);
+            Class<?> cls = Class.forName("sun.nio.ch.FileChannelImpl");
+            Method map0 = JavaInternals.getMethod(cls, "map0", int.class, long.class, long.class);
+            if (map0 != null) {
+                return (long) map0.invoke(f.getChannel(), mode, start, size);
+            }
+            // Newer JDK has an extra 'sync' argument
+            map0 = JavaInternals.getMethod(cls, "map0", int.class, long.class, long.class, boolean.class);
+            if (map0 != null) {
+                return (long) map0.invoke(f.getChannel(), mode, start, size, false);
+            }
+            throw new IllegalStateException("map0 method not found");
         } catch (InvocationTargetException e) {
             Throwable target = e.getTargetException();
             throw (target instanceof IOException) ? (IOException) target : new IOException(target);
@@ -179,8 +187,11 @@ public static void unmap(long start, long size) {
         }
 
         try {
-            Method unmap0 = Class.forName("sun.nio.ch.FileChannelImpl").getDeclaredMethod("unmap0", long.class, long.class);
-            unmap0.setAccessible(true);
+            Class<?> cls = Class.forName("sun.nio.ch.FileChannelImpl");
+            Method unmap0 = JavaInternals.getMethod(cls, "unmap0", long.class, long.class);
+            if (unmap0 == null) {
+                throw new IllegalStateException("unmap0 method not found");
+            }
             unmap0.invoke(null, start, size);
         } catch (ReflectiveOperationException e) {
             throw new IllegalStateException(e);
diff --git a/src/one/nio/mem/OffheapMap.java b/src/one/nio/mem/OffheapMap.java
index 4d80d50a..8727fddd 100755
--- a/src/one/nio/mem/OffheapMap.java
+++ b/src/one/nio/mem/OffheapMap.java
@@ -431,20 +431,24 @@ public void clear() {
     }
 
     public void iterate(Visitor<K, V> visitor) {
-        iterate(visitor, 0, 1);
+        iterate(visitor, 0, capacity, 1);
     }
 
     public void iterate(final Visitor<K, V> visitor, final int workers) {
         AsyncExecutor.fork(workers, new ParallelTask() {
             @Override
             public void execute(int taskNum, int taskCount) {
-                iterate(visitor, taskNum, taskCount);
+                iterate(visitor, taskNum, capacity, taskCount);
             }
         });
     }
 
-    public void iterate(Visitor<K, V> visitor, int taskNum, int taskCount) {
-        for (int i = taskNum; i < capacity; i += taskCount) {
+    public void iterate(Visitor<K, V> visitor, int start, int end, int step) {
+        if (start < 0 || end > capacity) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        for (int i = start; i < end; i += step) {
             long currentPtr = mapBase + (long) i * 8;
             RWLock lock = locks[i & (CONCURRENCY_LEVEL - 1)].lockRead();
             try {
@@ -458,20 +462,24 @@ public void iterate(Visitor<K, V> visitor, int taskNum, int taskCount) {
     }
 
     public void iterate(WritableVisitor<K, V> visitor) {
-        iterate(visitor, 0, 1);
+        iterate(visitor, 0, capacity, 1);
     }
 
     public void iterate(final WritableVisitor<K, V> visitor, final int workers) {
         AsyncExecutor.fork(workers, new ParallelTask() {
             @Override
             public void execute(int taskNum, int taskCount) {
-                iterate(visitor, taskNum, taskCount);
+                iterate(visitor, taskNum, capacity, taskCount);
             }
         });
     }
 
-    public void iterate(WritableVisitor<K, V> visitor, int taskNum, int taskCount) {
-        for (int i = taskNum; i < capacity; i += taskCount) {
+    public void iterate(WritableVisitor<K, V> visitor, int start, int end, int step) {
+        if (start < 0 || end > capacity) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        for (int i = start; i < end; i += step) {
             long currentPtr = mapBase + (long) i * 8;
             RWLock lock = locks[i & (CONCURRENCY_LEVEL - 1)].lockWrite();
             try {
@@ -543,7 +551,7 @@ public static class Record<K, V> {
         protected final RWLock lock;
         protected long entry;
 
-        protected Record(OffheapMap<K, V> map, RWLock lock, long entry) {
+        public Record(OffheapMap<K, V> map, RWLock lock, long entry) {
             this.map = map;
             this.lock = lock;
             this.entry = entry;
@@ -591,7 +599,7 @@ public static class WritableRecord<K, V> extends Record<K, V> {
         protected K key;
         protected long currentPtr;
 
-        protected WritableRecord(OffheapMap<K, V> map, RWLock lock, long entry, K key, long currentPtr) {
+        public WritableRecord(OffheapMap<K, V> map, RWLock lock, long entry, K key, long currentPtr) {
             super(map, lock, entry);
             this.key = key;
             this.currentPtr = currentPtr;
diff --git a/src/one/nio/mem/SharedMemoryFixedMap.java b/src/one/nio/mem/SharedMemoryFixedMap.java
index 88f26532..23d28728 100755
--- a/src/one/nio/mem/SharedMemoryFixedMap.java
+++ b/src/one/nio/mem/SharedMemoryFixedMap.java
@@ -35,7 +35,7 @@ protected SharedMemoryFixedMap(String fileName, long fileSize, int valueSize, lo
         this.allocator = createFixedSizeAllocator(getEntrySize(valueSize));
     }
 
-    private static int getEntrySize(int valueSize) {
+    protected static int getEntrySize(int valueSize) {
         return (valueSize + (HEADER_SIZE + 7)) & ~7;  // align to 8-byte boundary
     }