简单栈的数组实现

package com.yy.stack;


public class Stack {
	
	//数组实现栈结构
	private Object[] obj;
	//栈的长度
	private int index;
	
	/**
	 * 初始化长度为10的栈
	 */
	public Stack() {
		obj = new Object[10];
	}
	
	/**
	 * 初始化长度为length的栈
	 * @param length
	 */
	public Stack(int length){
		obj = new Object[length];
	}
	
	/**
	 * 进栈
	 */
	public void push(Object o){
		expandStack();
		obj[index++] = o;
	}

	/**
	 * 出栈
	 */
	public void pop(){
		//1.先判断数组是否为空
		//2.出栈
		if(isEmpty()){
			System.out.println("栈为空");
		}else{
			Object[] temp = new Object[index--];
			System.arraycopy(obj, 0, temp, 0, index);
			obj = temp;
		}
	}
	
	/**
	 * 出栈并返回数据
	 * @return
	 */
	public Object getPop(){
		Object o = null;
		if(isEmpty()){
			System.out.println("栈为空");
		}else{
			o = getLast();
			Object[] temp = new Object[index--];
			System.arraycopy(obj, 0, temp, 0, index);
			obj = temp;
		}
		return o;
	}

	/**
	 * 获取栈的最后一位数据
	 * @return
	 */
	public Object getLast() {
		int length = index;
		return obj[--length];
	}

	/**
	 * 判断是否为空栈
	 * @return
	 */
	public boolean isEmpty() {
		if(index == 0){
			return true;
		}
		return false;
	}

	/**
	 * 
	 * 判断栈的容量并扩大
	 */
	private void expandStack() {
		//判断当前栈的长度是否满了
		if(index >= obj.length){
			Object[] temp = new Object[obj.length * 2];
			System.arraycopy(obj, 0, temp, 0, obj.length);//数组拷贝
			obj = temp;
		}
	}

	
	/**
	 * 获取栈的长度
	 * @return
	 */
	public int getSize(){
		return index;
	}
	
	/**
	 * 打印栈
	 */
	public void printStack(){
		for(int i = 0; i < index; i++){
			System.out.println(obj[i]);
		}
	}
	
	public static void main(String[] args) {
		Stack s = new Stack();
		int i = 1;
		int j = 2;
		s.push(i);
		s.push(j);
		System.out.println(s.getPop());
		s.printStack();
	}
}