在 Java 中杀死线程
run()方法完成后，线程会自动销毁。但是它可能需要在线程完成其生命周期之前终止/停止线程。以前，方法暂停()、恢复()和停止()用于管理线程的执行。但是 Java 2 不赞成这些方法，因为它们可能导致系统故障。暂停/停止线程的现代方法是使用布尔标志和 Thread.interrupt()方法。
- 使用布尔标志:我们可以定义一个布尔变量，用于停止/终止线程，比如“退出”。每当我们想要停止一个线程时,“exit”变量将被设置为 true。
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to illustrate
// stopping a thread using boolean flag
class MyThread implements Runnable {
// to stop the thread
private boolean exit;
private String name;
Thread t;
MyThread(String threadname)
{
name = threadname;
t = new Thread(this, name);
System.out.println("New thread: " + t);
exit = false;
t.start(); // Starting the thread
}
// execution of thread starts from run() method
public void run()
{
int i = 0;
while (!exit) {
System.out.println(name + ": " + i);
i++;
try {
Thread.sleep(100);
}
catch (InterruptedException e) {
System.out.println("Caught:" + e);
}
}
System.out.println(name + " Stopped.");
}
// for stopping the thread
public void stop()
{
exit = true;
}
}
// Main class
public class Main {
public static void main(String args[])
{
// creating two objects t1 & t2 of MyThread
MyThread t1 = new MyThread("First thread");
MyThread t2 = new MyThread("Second thread");
try {
Thread.sleep(500);
t1.stop(); // stopping thread t1
t2.stop(); // stopping thread t2
Thread.sleep(500);
}
catch (InterruptedException e) {
System.out.println("Caught:" + e);
}
System.out.println("Exiting the main Thread");
}
}
Output:
New thread: Thread[First thread, 5, main]
New thread: Thread[Second thread, 5, main]
First thread: 0
Second thread: 0
First thread: 1
Second thread: 1
First thread: 2
Second thread: 2
First thread: 3
Second thread: 3
First thread: 4
Second thread: 4
First thread: 5
Second thread Stopped.
First thread Stopped.
Exiting the main Thread
注意:每次输出可能会有变化。 通过使用标志，我们可以随时停止线程，并且可以防止不必要的运行时错误。
- 使用易变布尔标志:我们也可以使用易变布尔标志来保证我们的代码线程安全。易失性变量直接存储在主内存中，这样线程就不能在本地缓存它的值。当多个线程正在访问同一个变量，并且一个线程所做的更改可能对其他线程不可见时，可能会出现这种情况。在这种情况下，我们可以使用易变的布尔标志。 让我们考虑下面使用非易失性布尔标志的代码:
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to illustrate non-volatile boolean flag
public class Main {
// static used here
// because a non-static variable
// cannot be referenced
// from a static context
// exit variable to stop both
// the main and inside threads
static boolean exit = false;
public static void main(String[] args)
{
System.out.println("started main thread..");
// a thread inside main thread
new Thread() {
public void run()
{
System.out.println("started inside thread..");
// inside thread caches the value of exit,
// so changes made to exit are not visible here
while (!exit) // will run infinitely
{
}
// this will not be printed.
System.out.println("exiting inside thread..");
}
}.start();
try {
Thread.sleep(500);
}
catch (InterruptedException e) {
System.out.println("Caught :" + e);
}
// so that we can stop the threads
exit = true;
System.out.println("exiting main thread..");
}
}
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