数据结构-栈实现（动态数组）

  动态数组和普通数组的区别是：普通数组定义好长度后不可改变，而动态数组会在数组满时修改数组的最大长度。

package stack;

import java.util.Scanner;

public class StackDemo1 {
    private int[] stack;//用数组模拟栈
    private int maxSize;//定义栈的大小
    private int top=-1;//定义栈顶

    //构造器
    StackDemo1(){

    }
    StackDemo1(int max){
        maxSize=max;
        stack=new int[maxSize];
    }
    //判断栈空
    boolean isEmpty(){
        return top==-1?true:false;//用三元运算符判断，空返回true
    }
    //判断栈满
    boolean isFull(){
        return top==maxSize-1?true:false;//用三元运算符判断，空返回true
    }
    //数组扩容
    public void doubleSize(){
        int[] newstackarray = new int[maxSize*2];//定义一个新数组，长度为二倍
        for(int i = 0;i<=top;i++){//把原先的栈赋值给新的栈
            newstackarray[i] = stack[i];
        }
        maxSize *=2;//重新规定栈的大小
        stack= newstackarray;//把新栈赋值给之前的栈
    }
    //存入数据
    public void push(int value){
        if(isFull()){
            doubleSize();
        }
        top++;
        stack[top]=value;
    }
    //取出数据
    public void pop(){
        if(!isEmpty()){
            System.out.println(stack[top]);
            top--;
        }else{
            throw new RuntimeException("数组空，不能取数据");
        }
    }
    //展示所有数据
    public void list(){
        if(isEmpty()){
            throw new RuntimeException("数组为空");
        }
        for(int i=0;i<=top;i++){
            System.out.printf("stack[%d]=%d",i,stack[i]);
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("输入栈的大小");
        StackDemo1 stackDemo = new StackDemo1(scanner.nextInt());
        while(true){
            System.out.println("pop取出数据");
            System.out.println("push存入数据");
            System.out.println("list展示数据");
            System.out.println("exit展示数据");
            System.out.println("输入一个数");
            String s=scanner.next();
            switch (s){
                case "pop":
                    stackDemo.pop();
                    break;
                case "push":
                    int s1=scanner.nextInt();
                    stackDemo.push(s1);
                    break;
                case "list":
                    stackDemo.list();
                    break;
                case "exit":
                    break;
            }
        }
    }

}