Make UnpooledDirectByteBuf, UnpooledHeapByteBuf and UnpooledUnsafeDirectByteBuf constructors public.

Motivation:

The constrcutors a protected atm but the classes are public. We should make the constructors public as well to make it easier to write your own ByteBufAllocator.

Modifications:

Change constructors to be public and add some javadocs.

Result:

Easier to create own ByteBufAllocator.

buffer/src/main/java/io/netty/buffer/UnpooledDirectByteBuf.java

@@ -28,9 +28,9 @@ import java.nio.channels.GatheringByteChannel;
 import java.nio.channels.ScatteringByteChannel;
 
 /**
- * A NIO {@link ByteBuffer} based buffer.  It is recommended to use {@link Unpooled#directBuffer(int)}
- * and {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the
- * constructor explicitly.
+ * A NIO {@link ByteBuffer} based buffer. It is recommended to use
+ * {@link UnpooledByteBufAllocator#directBuffer(int, int)}, {@link Unpooled#directBuffer(int)} and
+ * {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the constructor explicitly.
  */
 public class UnpooledDirectByteBuf extends AbstractReferenceCountedByteBuf {
 
@@ -47,7 +47,7 @@ public class UnpooledDirectByteBuf extends AbstractReferenceCountedByteBuf {
      * @param initialCapacity the initial capacity of the underlying direct buffer
      * @param maxCapacity     the maximum capacity of the underlying direct buffer
      */
-    protected UnpooledDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
+    public UnpooledDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
         super(maxCapacity);
         if (alloc == null) {
             throw new NullPointerException("alloc");

buffer/src/main/java/io/netty/buffer/UnpooledHeapByteBuf.java

@@ -30,7 +30,9 @@ import java.nio.channels.ScatteringByteChannel;
 import static io.netty.util.internal.ObjectUtil.checkNotNull;
 
 /**
- * Big endian Java heap buffer implementation.
+ * Big endian Java heap buffer implementation. It is recommended to use
+ * {@link UnpooledByteBufAllocator#heapBuffer(int, int)}, {@link Unpooled#buffer(int)} and
+ * {@link Unpooled#wrappedBuffer(byte[])} instead of calling the constructor explicitly.
  */
 public class UnpooledHeapByteBuf extends AbstractReferenceCountedByteBuf {
 
@@ -44,7 +46,7 @@ public class UnpooledHeapByteBuf extends AbstractReferenceCountedByteBuf {
      * @param initialCapacity the initial capacity of the underlying byte array
      * @param maxCapacity the max capacity of the underlying byte array
      */
-    protected UnpooledHeapByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
+    public UnpooledHeapByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
         super(maxCapacity);
 
         checkNotNull(alloc, "alloc");

buffer/src/main/java/io/netty/buffer/UnpooledUnsafeDirectByteBuf.java

@@ -28,9 +28,9 @@ import java.nio.channels.GatheringByteChannel;
 import java.nio.channels.ScatteringByteChannel;
 
 /**
- * A NIO {@link ByteBuffer} based buffer.  It is recommended to use {@link Unpooled#directBuffer(int)}
- * and {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the
- * constructor explicitly.
+ * A NIO {@link ByteBuffer} based buffer. It is recommended to use
+ * {@link UnpooledByteBufAllocator#directBuffer(int, int)}, {@link Unpooled#directBuffer(int)} and
+ * {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the constructor explicitly.}
  */
 public class UnpooledUnsafeDirectByteBuf extends AbstractReferenceCountedByteBuf {
 
@@ -48,7 +48,7 @@ public class UnpooledUnsafeDirectByteBuf extends AbstractReferenceCountedByteBuf
      * @param initialCapacity the initial capacity of the underlying direct buffer
      * @param maxCapacity     the maximum capacity of the underlying direct buffer
      */
-    protected UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
+    public UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
         super(maxCapacity);
         if (alloc == null) {
             throw new NullPointerException("alloc");