手写一个简单的栈（只为记录学习，新手勿喷）

public class ArrayStack{

private long[] a;
private int size;//指定栈大小
private int top;//栈顶

//初始化指定栈大小
public ArrayStack(int maxSize){
    this.size = maxSize;
    this.a = new long[size];
    this.top = -1;//代表空栈
}

//初始化不指定大小默认为1
public ArrayStack(){
    this.size = 1;
    this.a = new long[size];
    this.top = -1;
}

//入栈
public void push(long value){
    //判断栈是否满了
    if(isFull()){
        System.out.print("栈已满");
        return;
    }
    a[++top] = value;
}

//查出栈顶数据，不删除
public long peek(){
    //判断栈中是否有数据
    if(isEmpty()){
        System.out.print("栈中没有数据");
        return 0;
    }
    return a[top];
}

//查出栈顶数据, 并且删除
public void pop(){
    //判断栈中是否有数据
    if(isEmpty()){
        System.out.print("栈中没有数据");
        return 0;
    }
    return a[top--];
}

//查出栈的大小
public long size(){
    return top+1;
}

public boolean isEmpty(){
    return (top == -1);
}

public boolean isFull(){
    return (top == size-1);
}


public static void main(String[] args) {
	ArrayStack stack = new ArrayStack();
	System.out.println(stack.size());
	stack.push(1);
	System.out.println(stack.peek());
	stack.push(2);
}

}