1 files changed, 9 insertions, 6 deletions

diff --git a/java/src/main/java/com/google/protobuf/nano/MessageNano.java b/java/src/main/java/com/google/protobuf/nano/MessageNano.java
index e95c514..82dc6cc 100644
--- a/java/src/main/java/com/google/protobuf/nano/MessageNano.java
+++ b/java/src/main/java/com/google/protobuf/nano/MessageNano.java
@@ -67,16 +67,20 @@ public abstract class MessageNano {
     }
 
     /**
-     * Serializes the message and writes it to {@code output}.  This does not
-     * flush or close the stream.
+     * Serializes the message and writes it to {@code output}.
+     *
+     * @param output the output to receive the serialized form.
+     * @throws IOException if an error occurred writing to {@code output}.
      */
-    abstract public void writeTo(CodedOutputByteBufferNano output) throws java.io.IOException;
+    public void writeTo(CodedOutputByteBufferNano output) throws IOException {
+        // Does nothing by default. Overridden by subclasses which have data to write.
+    }
 
     /**
      * Parse {@code input} as a message of this type and merge it with the
      * message being built.
      */
-    abstract public MessageNano mergeFrom(final CodedInputByteBufferNano input) throws IOException;
+    public abstract MessageNano mergeFrom(CodedInputByteBufferNano input) throws IOException;
 
     /**
      * Serialize to a byte array.
@@ -95,9 +99,8 @@ public abstract class MessageNano {
      * write more than length bytes OutOfSpaceException will be thrown
      * and if length bytes are not written then IllegalStateException
      * is thrown.
-     * @return byte array with the serialized data.
      */
-    public static final void toByteArray(MessageNano msg, byte [] data, int offset, int length) {
+    public static final void toByteArray(MessageNano msg, byte[] data, int offset, int length) {
         try {
             final CodedOutputByteBufferNano output =
                 CodedOutputByteBufferNano.newInstance(data, offset, length);