ARROW-5434: [Memory][Java] Introduce wrappers for backward compatibility.

java/memory/src/main/java/io/netty/buffer/ArrowBuf.java

@@ -77,7 +77,7 @@ public final class ArrowBuf implements AutoCloseable {
   private int readerIndex;
   private int writerIndex;
   private final HistoricalLog historicalLog = BaseAllocator.DEBUG ?
-      new HistoricalLog(BaseAllocator.DEBUG_LOG_LENGTH, "ArrowBuf[%d]", id) : null;
+          new HistoricalLog(BaseAllocator.DEBUG_LOG_LENGTH, "ArrowBuf[%d]", id) : null;
   private volatile int length;
 
   /**
@@ -1204,4 +1204,51 @@ public ArrowBuf reallocIfNeeded(final int size) {
               "Realloc is only available in the context of operator's UDFs");
     }
   }
+
+  /**
+   * Following are wrapper methods to keep this backward compatible.
+   */
+  @Deprecated
+  public void release() {
+    referenceManager.release();
+  }
+
+  @Deprecated
+  public void release(int decrement) {
+    referenceManager.release(decrement);
+  }
+
+  @Deprecated
+  public void retain() {
+    referenceManager.retain();
+  }
+
+  @Deprecated
+  public void retain(int increment) {
+    referenceManager.retain(increment);
+  }
+
+  @Deprecated
+  public ArrowBuf clear() {
+    this.readerIndex = this.writerIndex = 0;
+    return this;
+  }
+
+  /**
+   * Initialize the reader and writer index.
+   * @param readerIndex index to read from
+   * @param writerIndex index to write to
+   * @return this
+   */
+  @Deprecated
+  public ArrowBuf setIndex(int readerIndex, int writerIndex) {
+    if (readerIndex >= 0 && readerIndex <= writerIndex && writerIndex <= this.capacity()) {
+      this.readerIndex = readerIndex;
+      this.writerIndex = writerIndex;
+      return this;
+    } else {
+      throw new IndexOutOfBoundsException(String.format("readerIndex: %d, writerIndex: %d " +
+       "(expected:0 <= readerIndex <= writerIndex <= capacity(%d))", readerIndex, writerIndex, this.capacity()));
+    }
+  }
 }

java/memory/src/main/java/io/netty/buffer/NettyArrowBuf.java

@@ -76,6 +76,10 @@ public ByteBuf retain() {
     return this;
   }
 
+  public ArrowBuf arrowBuf() {
+    return arrowBuf;
+  }
+
   @Override
   public ByteBuf retain(final int increment) {
     arrowBuf.getReferenceManager().retain(increment);
@@ -351,12 +355,12 @@ public int getBytes(int index, FileChannel out, long position, int length) throw
 
   @Override
   public int setBytes(int index, ScatteringByteChannel in, int length) throws IOException {
-    throw new UnsupportedOperationException("Operation not supported");
+    return (int) in.read(nioBuffers(index, length));
   }
 
   @Override
   public int setBytes(int index, FileChannel in, long position, int length) throws IOException {
-    throw new UnsupportedOperationException("Operation not supported");
+    return (int) in.read(nioBuffers(index, length));
   }
 
   @Override