我试图用Java构建一个基于文本的待办事项列表，但在显示项目时遇到了一些困难。
当我运行代码并输入“1”时，待办事项列表的内容会显示给我，但它们一直在循环，并且永远不会停止。我假设这与检查 userChoice 变量的 while 循环有关，但我的问题是为什么即使在 break 语句之后列表仍在不断重申？我希望发生的是输入一个数字，执行操作，然后再次显示指令提示。
java代码:
package com.company;
import java.util.ArrayList;
import java.util.Scanner;
public class Main {
// create an arraylist to store users items
static ArrayList<String> toDoList = new ArrayList<String>(3);
public static void main(String[] args) {
// greet the user
System.out.println("**Your To-Do list** \n");
// add default items to list
toDoList.add("Buy Groceries");
toDoList.add("Work Out");
toDoList.add("Play CS");
// user menu/instruction
System.out.println("Please select from one of the following options: \n 1. Show to-do list \n 2. Add item " +
"\n 3. Remove item \n 4. Exit program \n");
// prompt user for their choice
System.out.print("Enter your choice: ");
// get user choice
Scanner input = new Scanner(System.in);
int userChoice = input.nextInt();
while (userChoice != 4) {
switch (userChoice) {
case 1:
getToDoList();
break;
case 2:
// create method that allows you to add item to the toDolist
break;
case 3:
// create method that allows you to remove item from the toDolist
break;
case 4:
// create method that terminates application
break;
}
}
}
// method that returns contents of the list
public static void getToDoList(){
for (int i = 0; i < toDoList.size(); i++) {
System.out.println(toDoList.get(i));
}
}
}
这是因为您没有再次请求读取用户。
case 1:
getToDoList();
input.nextInt();
break;
或者将 input.nextInt（）; 移到开关块的外部（在其下方）。
因为 userChoice 始终为 1，所以它始终循环。
import java.util.ArrayList;
import java.util.Scanner;
public class Groceries {
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<String> a=new ArrayList<String>();
a.add("Food");
a.add("Furniture");
a.add("Plywood");
while(true)
{
System.out.println("Enter your choice");
System.out.println("Your choice List\n 1:getList 2.addinthelist 3.removefromlist 4.exit");
Scanner sc=new Scanner(System.in);
int a1=sc.nextInt();
switch(a1)
{
case 1:
System.out.println(a);
break;
case 2:
System.out.println("List before addition of elemnt is :"+a);
System.out.println("Enter element to be added into the string");
String sss=sc.next();
a.add(sss);
System.out.println("List after addition of element is :"+a);
break;
case 3:
System.out.println("List before deletion of elemnt is "+a);
System.out.println("Enter an index of an element to be removed");
int abc=sc.nextInt();
a.remove(abc);
System.out.println("List after Deletion of an element is "+a);
break;
case 4:
System.exit(0);
default:
System.out.println("You entered wrong number !! Please enter 4 to exit");
}
}
}
}
