I. API

public void interrupt()

public static boolean interrupted()

public boolean isInterrupted()

II. Description of interrupt

1. Introduction

The call of the following methods will make the current thread enter the blocking state, and the blocking can be interrupted by calling the interrupt method of the current thread

Object # wait # method

Thread # sleep # method

Thread # join # method

io# operation of interruptible channel #

The # wakeup # method of Selector #

Several other methods

All of the above methods will make the current thread into blocking, so this method is sometimes called interruptible method. Interrupting a thread does not mean the end of the thread's life cycle, but only the blocking state of the current thread.

Once the thread is interrupted in the case of blocking, an exception called InterruptedException will be thrown. This exception is like a signal to inform the current thread that it has been interrupted.

2. Actual combat

package concurrent;

import java.util.concurrent.TimeUnit;

public class ThreadInterrptu {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            try {
                TimeUnit.MINUTES.sleep(1);
            } catch (InterruptedException e) {
                System.out.println("I am be interruputed");
                e.printStackTrace();
            }
        });
        thread.start();
        try {
            TimeUnit.MILLISECONDS.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        thread.interrupt();
    }
}

3. Test

I am be interruputed

java.lang.InterruptedException: sleep interrupted

    at java.lang.Thread.sleep(Native Method)

    at java.lang.Thread.sleep(Thread.java:340)

    at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)

    at concurrent.ThreadInterrptu.lambda$main$0(ThreadInterrptu.java:9)

    at java.lang.Thread.run(Thread.java:748)

4. Description

The program creates a thread and attempts to sleep for 1 minute, but it is interrupted by the main thread calling the # interrupt # method after about 2 milliseconds. The execution result of the program is # I am be interrupted.

If a thread is already in a dead state, an attempt to interrupt it will be ignored.

III. isInterrupted description

Interrupted ， is a member method of ， Thread ， which mainly judges whether the current Thread is interrupted. This method is only a judgment on the interrupt identification of the current Thread and will not affect any change in the identification.

1. Code

package concurrent;

import java.util.concurrent.TimeUnit;

public class ThreadisInterrupted {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            while (true) {
            }
        });
        thread.start();
        try {
            TimeUnit.MILLISECONDS.sleep(2);
            System.out.println("Thread is interrupted?" + thread.isInterrupted());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        thread.interrupt();
        System.out.println("Thread is interrupted?" + thread.isInterrupted());
    }
}

2. Test

Thread is interrupted?false

Thread is interrupted?true

Make a slight change to the above code and change the loop execution to the interruptible method of "sleep", which will capture the interrupt signal and erase the "interrupt" flag.

package concurrent;

import java.util.concurrent.TimeUnit;

public class ThreadisInterrupted2 {
    public static void main(String[] args) {
        Thread thread = new Thread() {
            public void run() {
                while (true) {
                    try {
                        TimeUnit.MINUTES.sleep(1);
                    } catch (InterruptedException e) {
                        System.out.println("Thread is interrupted?" + isInterrupted());
                    }
                }
            }
        };

        thread.setDaemon(true);
        thread.start();
        try {
            TimeUnit.MILLISECONDS.sleep(2);
            System.out.println("Thread is interrupted?" + thread.isInterrupted());
        } catch (
                InterruptedException e) {
            e.printStackTrace();
        }
        thread.interrupt();
        try {
            TimeUnit.MILLISECONDS.sleep(2);
            System.out.println("Thread is interrupted?" + thread.isInterrupted());
        } catch (
                InterruptedException e) {
            e.printStackTrace();
        }
    }
}

The test results are as follows:

Thread is interrupted?false

Thread is interrupted?false

Thread is interrupted?false

Because the interruptible method "sleep" is used in the "run" method, it will capture the interrupt signal and erase the "interrupt" identification, so the program execution result is "false"

IV. description of interrupted

1. Description

Interrupted is a static method. Although it is also used to judge whether the current thread is interrupted, it is very different from the member method ， isInterrupted ， method. Calling this method will directly erase the interrupt ID of the thread. If the current thread is interrupted, the first call of ， interrupted ， method will return ， true, And erase the interrupt identifier immediately, and the subsequent invocation will always return to false unless it is interrupted again.

2. Code

package concurrent;

import java.util.concurrent.TimeUnit;

public class ThreadisInterrupted3 {
    public static void main(String[] args) {
        Thread thread = new Thread() {
            public void run() {
                while (true) {
                    System.out.println(Thread.interrupted());
                }
            }
        };

        thread.setDaemon(true);
        thread.start();
        try {
            TimeUnit.MILLISECONDS.sleep(2);
        } catch (
                InterruptedException e) {
            e.printStackTrace();
        }
        thread.interrupt();
    }
}

3. Test

false

false

false

false

false

false

true

false

false

false

false

false

false

Appears only once