java模拟堆栈

import java.util.List;
import java.util.ArrayList;


public class StackS {

private long size; //栈的大小
private List<Object> stacks = new ArrayList<Object>(); //栈

/**
* 初始化栈
* @param size
*/
public StackS(long size){
this.size = size;
}
/**
* 入栈
* @param obj
*/
public void push(Object obj){
if (this.stacks.size() < this.size) {
this.stacks.add(obj);
}else{
System.out.println("栈已满。。。。。。");
}
}
/**
* 出栈
* @return
*/
public Object pop(){
Object obj;
if (!this.isEmpty()) {
System.out.println("栈为空。。。。。。");
obj = null;
}else{
obj = this.peek();
this.stacks.remove(this.stacks.size() - 1);
}
return obj;
}
/**
* 判断栈是否为空
* @return
*/
public boolean isEmpty(){
return this.stacks.size() <= 0 ? false : true;
}
/**
* 判断栈是否为满
* @return
*/
public boolean isFull(){
return this.stacks.size() == this.size ? true : false;
}
/**
* 获取栈顶元素
* @return
*/
public Object peek(){
Object obj;
if (!this.isEmpty()) {
System.out.println("栈为空。。。。。。");
obj = null;
}else{
obj = this.stacks.get(this.stacks.size() - 1);
}
return obj;
}
/**
* 获取栈大小
* @return
*/
public long size(){
return this.stacks.size();
}
}