HADOOP-8297. Writable javadocs don't carry default constructor (harsh)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1338557 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -65,6 +65,8 @@ Trunk (unreleased changes)
 
     HADOOP-8308. Support cross-project Jenkins builds. (tomwhite)
 
+    HADOOP-8297. Writable javadocs don't carry default constructor (harsh)
+
   BUG FIXES
 
     HADOOP-8177. MBeans shouldn't try to register when it fails to create MBeanName.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Writable.java

@@ -43,6 +43,9 @@ import org.apache.hadoop.classification.InterfaceStability;
  *       private int counter;
  *       private long timestamp;
  *
+ *       // Default constructor to allow (de)serialization
+ *       MyWritable() { }
+ *
  *       public void write(DataOutput out) throws IOException {
  *         out.writeInt(counter);
  *         out.writeLong(timestamp);