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    package org.apache.hadoop.hdfs.util;
019    
020    /**
021     * A Holder is simply a wrapper around some other object. This is useful
022     * in particular for storing immutable values like boxed Integers in a
023     * collection without having to do the "lookup" of the value twice.
024     */
025    public class Holder<T> {
026      public T held;
027      
028      public Holder(T held) {
029        this.held = held;
030      }
031      
032      @Override
033      public String toString() {
034        return String.valueOf(held);
035      }
036    }