java 如何在扫描仪获得输入之前运行一段时间？
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How to make a while to run until scanner get input?
提问by Xenovoyance
I'm trying to write a loop which runs until I type a specific text in console where the application is running. Something like:
我正在尝试编写一个循环，直到我在应用程序运行的控制台中键入特定文本为止。就像是：
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
}}
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?
而且我希望它每次通过时都写一行，所以我不希望它在一段时间内停止并等待下一个输入。我需要为此使用多个线程吗？
采纳答案by aioobe
Do I need to use multiple threads for this?
我需要为此使用多个线程吗？
Yes.
是的。
Since using a Scanneron System.inimplies that you're doing blocking IO, one thread will need to be dedicated for the task of reading user input.
由于使用ScanneronSystem.in意味着您正在执行阻塞 IO，因此需要一个线程专用于读取用户输入的任务。
Here's a basic example to get you started (I encourage you to look into the java.util.concurrentpackage for doing these type of things though.):
这是一个让您入门的基本示例（不过，我鼓励您查看java.util.concurrent用于执行此类操作的软件包。）：
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.
}
}
回答by Mark Peters
Yes, you would need two threads for this. The first could do something like this:
是的，为此您需要两个线程。第一个可以做这样的事情：
//accessible from both threads
CountDownLatch latch = new CountDownLatch(1);
//...
while ( true ) {
System.out.println("Waiting for input...");
if ( latch.await(2, TimeUnit.SECONDS) ) {
break;
}
}
And the other:
和另外一个：
Scanner scanner = new Scanner(System.in);
while ( !"STOP".equalsIgnoreCase(scanner.nextLine()) ) {
}
scanner.close();
latch.countDown();
