如何在扫描仪输入之前运行一段时间？ [英] How to make a while to run until scanner get input?

问题描述

我正在尝试编写一个循环，直到我在运行应用程序的控制台中键入特定文本。类似于：

I'm trying to write a loop which runs until I type a specific text in console where the application is running. Something like:

while (true) {
try {
    System.out.println("Waiting for input...");
    Thread.currentThread();
    Thread.sleep(2000);
    if (input_is_equal_to_STOP){ // if user type STOP in terminal
        break;
    }
} catch (InterruptedException ie) {
    // If this thread was intrrupted by nother thread
}}

我想让它在每次通过时写一行，所以我不希望它在一段时间内停止并等待下一个输入。我需要使用多个线程吗？

And I want it to write a line each time it pass through so I do not want it to stop within the while and wait for next input. Do I need to use multiple threads for this?

推荐答案

我需要使用吗？这个多线程？

是。

自在 System.in 上使用 Scanner 意味着你正在阻止IO，一个线程需要专门用于阅读用户输入的任务。

Since using a Scanner on System.in implies that you're doing blocking IO, one thread will need to be dedicated for the task of reading user input.

这是一个让你入门的基本例子（我鼓励你去研究 java.util.concurrent 用于执行这些类型的东西的包。）：

Here's a basic example to get you started (I encourage you to look into the java.util.concurrent package for doing these type of things though.):

import java.util.Scanner;

class Test implements Runnable {

    volatile boolean keepRunning = true;

    public void run() {
        System.out.println("Starting to loop.");
        while (keepRunning) {
            System.out.println("Running loop...");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
        }
        System.out.println("Done looping.");
    }

    public static void main(String[] args) {

        Test test = new Test();
        Thread t = new Thread(test);
        t.start();

        Scanner s = new Scanner(System.in);
        while (!s.next().equals("stop"));

        test.keepRunning = false;
        t.interrupt();  // cancel current sleep.
    }
}

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