时间戳

首页 > 解决方案 > 使用 ArrayList 显示另一个类的值

java - 使用 ArrayList 显示另一个类的值

问题描述

我正在尝试制作一个待办事项列表，要求您一项一项地输入您的任务，然后按顺序显示它们（如 1.task1、2.task 2、3.task 3 等）。但是当它显示任务时，它一次返回为“0.null”，而不是列出任何输入的任务。这是我正在使用的脚本：

一级

package todolist;
import java.util.ArrayList;

public class ToDoList1 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        ArrayList<ToDoList2> list = new ArrayList<ToDoList2>();
        System.out.println("Time to make a digital to-do list!");

        ToDoList2 n = new ToDoList2();
        list.add(n);

        System.out.println(ToDoList2.name + "'s to-do list");
        System.out.println(ToDoList2.i + ". " + ToDoList2.l);

        for(ToDoList2 enhanced : list)
        {
            System.out.println(ToDoList2.i + ". " + ToDoList2.m);
        }
    }
}

二等

package todolist;
import java.util.Scanner;

public class ToDoList2 {
    public static String name;
    public static int i;
    public static String l;
    public static String m;

    {
        Scanner s = new Scanner(System.in);
        System.out.println("First type your name to identify your list in case you lose it");
        name = s.nextLine();
        System.out.println("Make sure to type \"end\" when you are finished");    
        System.out.println("Type in the first item on your to-do list");
        String l = s.nextLine();
    }

    public ToDoList2() 
    {
        Scanner s = new Scanner(System.in);    
        for(int i = 1; i == i; i++)
        {
            System.out.println("Type in the next item for your to-do list");
            String m = s.nextLine();
            if("end".equals(m))
            {
                break;
            }
        }
    }
}

标签： javaarraylist

解决方案

您的代码不正确。ToDoList2 从标准输入扫描项目列表但不存储它。你应该做如下


import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class TodoList {

    public static String name;

    List<String> tasks;

    public TodoList(String name) {
        this.name = name;
        this.tasks = new ArrayList<>();
    }

    public void addTask(String task) {
        this.tasks.add(task);
    }

    public String toString() {
        int i = 1;
        StringBuilder stringBuilder = new StringBuilder();
        for (String task : tasks) {
            stringBuilder.append(i + ". " + task);
            stringBuilder.append("\n");
            i++;
        }
        return stringBuilder.toString();
    }

}

public class Main {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        System.out.println("First type your name to identify your list in case you lose it");
        String name = s.nextLine();

        System.out.println("Make sure to type \"end\" when you are finished");
        System.out.println("Type in the first item on your to-do list");

        TodoList todoList = new TodoList(name);

        String task = null;
        while (!(task = s.nextLine()).equals("end")) {
            todoList.addTask(task);
            System.out.println("Type in the next item for your to-do list");
        }

        System.out.println(todoList);

    }


}

推荐阅读