**Java源碼之Stack**
轉載請注明出處：[http://blog.csdn.net/itismelzp/article/details/50371987](http://blog.csdn.net/itismelzp/article/details/50371987)
Stack的源碼較短，在這里直接貼出：
Stack繼承自Vetor實現的，所以基礎的策略也來自Vector
~~~
/*
* 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 java.util;
/**
* {@code Stack} is a Last-In/First-Out(LIFO) data structure which represents a
* stack of objects. It enables users to pop to and push from the stack,
* including null objects. There is no limit to the size of the stack.
*/
public class Stack<E> extends Vector<E> {
private static final long serialVersionUID = 1224463164541339165L;
/**
* Constructs a stack with the default size of {@code Vector}.
*/
public Stack() {
}
/**
* 調用父類方法isEmpty判斷
*/
public boolean empty() {
return isEmpty();
}
/**
* 返回棧頂元素（元素不刪除）
*/
@SuppressWarnings("unchecked")
public synchronized E peek() {
try {
return (E) elementData[elementCount - 1]; // elementData見Vector
} catch (IndexOutOfBoundsException e) {
throw new EmptyStackException();
}
}
/**
* 刪除棧頂元素，并返回頂棧元素
*/
@SuppressWarnings("unchecked")
public synchronized E pop() {
if (elementCount == 0) {
throw new EmptyStackException();
}
final int index = --elementCount;
final E obj = (E) elementData[index];
elementData[index] = null;
modCount++;
return obj;
}
/**
* 元素入棧
*/
public E push(E object) {
addElement(object); // 依然是父類方法addElement
return object;
}
/**
* 返回元素在棧中的索引（棧頂元素索引為0，往下遞增）
*/
public synchronized int search(Object o) {
final Object[] dumpArray = elementData;
final int size = elementCount;
if (o != null) {
for (int i = size - 1; i >= 0; i--) {
if (o.equals(dumpArray[i])) {
return size - i;
}
}
} else {
for (int i = size - 1; i >= 0; i--) {
if (dumpArray[i] == null) {
return size - i;
}
}
}
return -1;
}
}
~~~
