001/** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019package org.apache.hadoop.mapreduce; 020 021import java.io.DataInput; 022import java.io.DataOutput; 023import java.io.IOException; 024 025import org.apache.hadoop.classification.InterfaceAudience; 026import org.apache.hadoop.classification.InterfaceStability; 027import org.apache.hadoop.io.WritableComparable; 028 029/** 030 * A general identifier, which internally stores the id 031 * as an integer. This is the super class of {@link JobID}, 032 * {@link TaskID} and {@link TaskAttemptID}. 033 * 034 * @see JobID 035 * @see TaskID 036 * @see TaskAttemptID 037 */ 038@InterfaceAudience.Public 039@InterfaceStability.Stable 040public abstract class ID implements WritableComparable<ID> { 041 protected static final char SEPARATOR = '_'; 042 protected int id; 043 044 /** constructs an ID object from the given int */ 045 public ID(int id) { 046 this.id = id; 047 } 048 049 protected ID() { 050 } 051 052 /** returns the int which represents the identifier */ 053 public int getId() { 054 return id; 055 } 056 057 @Override 058 public String toString() { 059 return String.valueOf(id); 060 } 061 062 @Override 063 public int hashCode() { 064 return id; 065 } 066 067 @Override 068 public boolean equals(Object o) { 069 if (this == o) 070 return true; 071 if(o == null) 072 return false; 073 if (o.getClass() == this.getClass()) { 074 ID that = (ID) o; 075 return this.id == that.id; 076 } 077 else 078 return false; 079 } 080 081 /** Compare IDs by associated numbers */ 082 public int compareTo(ID that) { 083 return this.id - that.id; 084 } 085 086 public void readFields(DataInput in) throws IOException { 087 this.id = in.readInt(); 088 } 089 090 public void write(DataOutput out) throws IOException { 091 out.writeInt(id); 092 } 093 094}