栈

package com.sjtu.design.excise;

//栈类

/**

 * 

 * @author tsh11089

 *

 */

public class SqStack {

private Object[] stackElem;

private int top;

// 初始化栈

public SqStack(int maxStack) {

stackElem = new Object[maxStack];

top = 0;

}

// 入栈

public void push(Object stack) {

if (top == stackElem.length) {

// throw new Exception("栈已满!");

System.out.println("栈已满!");

} else {

stackElem[top++] = stack;

}

}

// 出栈

public Object pop() {

if (top == 0) {

// throw new Exception("栈为空!");

System.out.println("栈为空!");

return null;

} else {

return stackElem[--top];// 删除然后返回现在的栈顶

}

}

// 打印(从栈顶到栈底)

public void display() {

for (int i = length() - 1; i >= 0; i--) {

System.out.print(stackElem[i] + " ");

}

System.out.println();

}

// 元素个数

public int length() {

return top;

}

// 栈顶

public Object peek() {

if (!isEmpty())

return stackElem[top - 1];

else

return null;

}

// 清空

public void clear() {

top = 0;

}

// 释放栈内存空间

public void free(SqStack stack) {

if (stack != null) {

stack = null;

}

}

// 栈空

public boolean isEmpty() {

return top == 0;

}

// 栈满

public boolean isFull() {

return top == stackElem.length;

}

public static void main(String[] args) {

SqStack sqStack1 = new SqStack(3);

sqStack1.push(1);

sqStack1.push(4);

sqStack1.push(7);

System.out.print("打印输出：  ");

sqStack1.display();

int top1 = (Integer) sqStack1.peek();

System.out.println("栈顶:  " + top1);

sqStack1.pop();

System.out.print("弹出栈顶，打印输出:  ");

sqStack1.display();

System.out.println("---------------------------------------");

SqStack sqStack2 = new SqStack(2);

sqStack2.push(2);

sqStack2.push(5);

sqStack2.push(8);

System.out.print("打印输出：  ");

sqStack2.display();

int top2 = (Integer) sqStack2.peek();

System.out.println("栈顶:  " + top2);

sqStack2.pop();

System.out.print("弹出栈顶，打印输出:  ");

sqStack2.display();

System.out.println("---------------------------------------");

SqStack sqStack3 = new SqStack(0);

sqStack3.push(3);

sqStack3.push(6);

sqStack3.push(9);

System.out.print("打印输出：  ");

sqStack3.display();

int top3 = (Integer) sqStack3.peek();

System.out.println("栈顶:  " + top3);

sqStack3.pop();

System.out.print("弹出栈顶，打印输出:  ");

sqStack3.display();

}

}