WritableComparable

官方给例子  做hadoop开发的都知道
WritableComparable没有自己的方法体。

    public class MyWritableComparable implements WritableComparable {
       // Some data
       private int counter;
       private long timestamp;
      
       public void write(DataOutput out) throws IOException {
         out.writeInt(counter);
         out.writeLong(timestamp);
       }
      
       public void readFields(DataInput in) throws IOException {
         counter = in.readInt();
         timestamp = in.readLong();
       }
      
       public int compareTo(MyWritableComparable w) {
         int thisValue = this.value;
         int thatValue = ((IntWritable)o).value;
         return (thisValue < thatValue ? -1 : (thisValue==thatValue ? 0 : 1));
       }
     }

一般序列化的类都会继承这个类型  有图为证。
看附件
http://dl2.iteye.com/upload/attachment/0096/8231/68aca470-285e-3c20-9a78-51828497e3a3.jpg