用这个程序迭代和使用 switch case

Question

如果有无效的选择，我想重复您的选择选项，但它正在退出。

谁能帮忙？

class Stackdemo1 {
    public static void main(String []args)throws IOException {
        Stack<Integer> st=new Stack<Integer>();
        BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
        int element,pos;
        int choice=0;  
        while(choice<4) {
            System.out.println("stack operation");
            System.out.println("1 push element");
            System.out.println("2 pop element");
            System.out.println("3 search for element");
            System.out.println("4 exit");
            System.out.println("your choice");
            choice=Integer.parseInt(br.readLine());

            switch(choice) {
                case 1:
                    System.out.print("enter element:");
                    element =Integer.parseInt(br.readLine());
                    st.push(element);
                    break;
                case 2:
                    Integer i=st.pop();
                    System.out.print("poped="+i);
                    break;
                case 3:
                    System.out.print("enter element");
                    element=Integer.parseInt(br.readLine());
                    pos=st.search(element);

                    if(pos== -1)
                        {
                             System.out.println("element not found");
                        } else
                             System.out.println("element found position:"+pos);
                    break;
                 default:
                    System.out.println("enter other number");     
                    continue;                          

             }
             System.out.println("Stack="+st);
        }
    }       
}

输出：

    D:\work>javac Stackdemo1.java

    D:\work>java Stackdemo1
    stack operation
    1 push element
    2 pop element
    3 search for element
    4 exit
    your choice
    5
    enter other number

Answer 1

您已输入 5 作为值，并且在循环条件下它是 while(choice