hashMap怎么实现

发布网友 发布时间：2022-04-24 02:47

我来回答

共2个回答

热心网友 时间：2022-04-06 03:19

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections.map;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Map;

/**
* A <code>Map</code> implementation that is a general purpose alternative
* to <code>HashMap</code>.
* <p>
* This implementation improves on the JDK1.4 HashMap by adding the
* {@link org.apache.commons.collections.MapIterator MapIterator}
* functionality and many methods for subclassing.
* <p>
* <strong>Note that HashedMap is not synchronized and is not thread-safe.</strong>
* If you wish to use this map from multiple threads concurrently, you must use
* appropriate synchronization. The simplest approach is to wrap this map
* using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
* exceptions when accessed by concurrent threads without synchronization.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class HashedMap
extends AbstractHashedMap implements Serializable, Cloneable {

/** Serialisation version */
private static final long serialVersionUID = -1788199231038721040L;

/**
* Constructs a new empty map with default size and load factor.
*/
public HashedMap() {
super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
}

/**
* Constructs a new, empty map with the specified initial capacity.
*
* @param initialCapacity the initial capacity
* @throws IllegalArgumentException if the initial capacity is less than one
*/
public HashedMap(int initialCapacity) {
super(initialCapacity);
}

/**
* Constructs a new, empty map with the specified initial capacity and
* load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is less than one
* @throws IllegalArgumentException if the load factor is less than zero
*/
public HashedMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}

/**
* Constructor copying elements from another map.
*
* @param map the map to copy
* @throws NullPointerException if the map is null
*/
public HashedMap(Map map) {
super(map);
}

//-----------------------------------------------------------------------
/**
* Clones the map without cloning the keys or values.
*
* @return a shallow clone
*/
public Object clone() {
return super.clone();
}

/**
* Write the map out using a custom routine.
*/
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
doWriteObject(out);
}

/**
* Read the map in using a custom routine.
*/
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
doReadObject(in);
}

}

热心网友 时间：2022-04-06 04:37

Map map = new HashMap();
还是你打算自己做一个？追问怎么实现的？

追答看源码吧太长贴不出来 关键是put 和 get 方法的实现
或者你自己做个一类 继承Map 各种Map子类区别的方法你就都知道了