栈

数组栈

初始化

private int top=-1;//top表示栈顶 -1
//    private int bottom=-1;
    private int[] stack;//数组模拟栈，数据放在数组中
    private int maxsize;

    public ArrayStack(int maxsize) {
        this.maxsize = maxsize;
        stack = new int[maxsize];
    }

1.栈满

//    栈满
public boolean isFull() {
    return top == maxsize - 1;
}

2.栈空

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

3.入栈

//    入栈
public void push(int data) {
    if (isFull()){
        throw new RuntimeException("栈满");
    }
    stack[++top] = data;
}

4.出栈

//    出栈
public int pop() {
    if (isEmpty())
        throw new RuntimeException("栈空");
    return stack[top--];
}

5.栈顶

//    栈顶数据
    public int peek(){
        if (isEmpty())
            throw new RuntimeException("栈空");
        return stack[top];
    }

6.遍历

//    遍历
    public void printStack(){
        if (isEmpty())
            throw new RuntimeException("栈空");
//        栈顶出，所以从top开始遍历
        for (int i = top; i >=0 ; --i) {
            System.out.printf("stack[%d]=%d\n",i,stack[i]);
        }
    }

7.测试

public class ArrayStackDemo {
    public static void main(String[] args) {
        ArrayStack arrayStack = new ArrayStack(3);
        String key="";
        boolean loop=true;
        Scanner scanner = new Scanner(System.in);
        while (loop){
            System.out.println("show");
            System.out.println("exit");
            System.out.println("push");
            System.out.println("peek");
            System.out.println("pop");
            System.out.print("请输入你的选择：");
            key=scanner.next();
            switch (key){
                case "show":
                    try {
                        arrayStack.printStack();
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "push":
                    try {
                        System.out.print("请输入你要push的数：");
                        int value=scanner.nextInt();
                        arrayStack.push(value);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "peek":
                    int peek = arrayStack.peek();
                    System.out.println("栈顶元素是："+peek);
                    break;
                case "pop":
                    try {
                        int res = arrayStack.pop();
                        System.out.println("出栈的数是："+res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "exit":
                    scanner.close();
                    loop=false;
                    break;
                default:
                    System.out.println("您的输入有误，请输入以下选项：");
            }
        }
        System.out.println("程序退出~~~~");
    }
}

链栈

在LinkedListStack类中定义一个Node成员内部类

1.Node类

private Node top;

private class Node {
    private int data;
    private Node next;

    public Node(int data) {
        this.data = data;
        this.next = null;
    }
}

2.入栈

//  入栈
    public void push(int data) {
        Node newNode = new Node(data);
        if (top == null) {
            top = newNode;
        } else {
            newNode.next = top;
            top = newNode;
        }
    }

3.出栈

//    出栈
    public int pop(){
        if (top==null){
            throw new RuntimeException("栈空");
        }
        int data=top.data;
        top=top.next;
        return data;
    }

4.栈顶

//    栈顶元素
    public int peek(){
        if (top==null)
            throw new RuntimeException("栈空");
        return top.data;
    }

5.栈空

//    栈空
    public boolean isEmpty(){
        return top==null;
    }

6.遍历

//    遍历
    public void printStack(){
//        top指针不能动，需要一个current的辅助指针
        Node current=top;
        if (top==null)
            throw new RuntimeException("栈空");
        while (current!=null){
            System.out.print(current.data+" ");
            current=current.next;
        }
        System.out.println();
    }

7.测试同数组栈一样