Java線程中的interrupt方法解讀

更新時間：2023年10月17日 08:40:35 作者：huskyui

這篇文章主要介紹了Java線程中的interrupt方法解讀,Java中的interrupt是一種線程間通信的機制，用于請求中斷線程的執(zhí)行。當一個線程調(diào)用另一個線程的interrupt()方法時，被調(diào)用線程會收到一個中斷信號，可以根據(jù)需要做出相應的處理,需要的朋友可以參考下

interrupt方法

首先梳理Thread關于interrupt的定義

/**
 * Interrupts this thread.
 *
 * <p> Unless the current thread is interrupting itself, which is
 * always permitted, the {@link #checkAccess() checkAccess} method
 * of this thread is invoked, which may cause a {@link
 * SecurityException} to be thrown.
 *
 * <p> If this thread is blocked in an invocation of the {@link
 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
 * class, or of the {@link #join()}, {@link #join(long)}, {@link
 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
 * methods of this class, then its interrupt status will be cleared and it
 * will receive an {@link InterruptedException}.
 *
 * <p> If this thread is blocked in an I/O operation upon an {@link
 * java.nio.channels.InterruptibleChannel InterruptibleChannel}
 * then the channel will be closed, the thread's interrupt
 * status will be set, and the thread will receive a {@link
 * java.nio.channels.ClosedByInterruptException}.
 *
 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
 * then the thread's interrupt status will be set and it will return
 * immediately from the selection operation, possibly with a non-zero
 * value, just as if the selector's {@link
 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
 *
 * <p> If none of the previous conditions hold then this thread's interrupt
 * status will be set. </p>
 *
 * <p> Interrupting a thread that is not alive need not have any effect.
 *
 * @throws  SecurityException
 *          if the current thread cannot modify this thread
 *
 * @revised 6.0
 * @spec JSR-51
 */
public void interrupt()

這里講述了Thread實例對象調(diào)用方法interrupt,有這幾種情況

? 1.在線程里面有wait,sleep,join方法,會彈出InterruptedException,狀態(tài)會被清除

? 2.io里面,會彈出異常,狀態(tài)會被設置,…

? 3.如果線程阻塞在nio中的Selector中,狀態(tài)會被設置,…

? 4.如果不是上面,這些情況,狀態(tài)會被設置

可以看出interrupt是關于狀態(tài)的設置

我們來驗證一下

第一種,沒有任何情況的

public static void main(String[] args) {
    Thread t1 = new Thread(()->{
       while(true){
           if (interrupted()) {
               break;
           }
           System.out.println("i" + new Date());
       }
    });
    t1.start();
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    t1.interrupt();
}

線程會在(1000+)ms后結束,整個程序也會結束

第二種,有sleep的情況下

public static void main(String[] args) {
    Thread t1 = new Thread(()->{
       while(true){
           if (interrupted()) {
               break;
           }
           try {
               Thread.sleep(100);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }

           System.out.println("i" + new Date());
       }
    });
    t1.start();
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    t1.interrupt();
}

方法并不會退出,只是打出了一個InterruptException

如何處理中斷？

上文都在介紹如何獲取中斷狀態(tài)，那么當我們捕獲到中斷狀態(tài)后，究竟如何處理呢？
Java類庫中提供的一些可能會發(fā)生阻塞的方法都會拋InterruptedException異常，如：BlockingQueue#put、BlockingQueue#take、Object#wait、Thread#sleep。
當你在某一條線程中調(diào)用這些方法時，這個方法可能會被阻塞很長時間，你可以在別的線程中調(diào)用當前線程對象的interrupt方法觸發(fā)這些函數(shù)拋出InterruptedException異常。
當一個函數(shù)拋出InterruptedException異常時，表示這個方法阻塞的時間太久了，別人不想等它執(zhí)行結束了。
當你的捕獲到一個InterruptedException異常后，亦可以處理它，或者向上拋出。
拋出時要注意？？？：當你捕獲到InterruptedException異常后，當前線程的中斷狀態(tài)已經(jīng)被修改為false(表示線程未被中斷)；此時你若能夠處理中斷，則不用理會該值；但如果你繼續(xù)向上拋InterruptedException異常，你需要再次調(diào)用interrupt方法，將當前線程的中斷狀態(tài)設為true。
注意：絕對不能“吞掉中斷”！即捕獲了InterruptedException而不作任何處理。這樣違背了中斷機制的規(guī)則，別人想讓你線程中斷，然而你自己不處理，也不將中斷請求告訴調(diào)用者，調(diào)用者一直以為沒有中斷請求。

更新相關interrupt方法的意義

public void interrupt()

Thread里面的打斷函數(shù),可以使用新建一個Thread對象,執(zhí)行thread.interrupt();

修改調(diào)用線程的interrupt 的status

public static boolean interrupted()

該方法可以判斷是否被打斷,但是這個interrupt的status會被清除,

/**
     * Tests whether the current thread has been interrupted.  The
     * <i>interrupted status</i> of the thread is cleared by this method.  In
     * other words, if this method were to be called twice in succession, the
     * second call would return false (unless the current thread were
     * interrupted again, after the first call had cleared its interrupted
     * status and before the second call had examined it).
     *
     * <p>A thread interruption ignored because a thread was not alive
     * at the time of the interrupt will be reflected by this method
     * returning false.
     *
     * @return  <code>true</code> if the current thread has been interrupted;
     *          <code>false</code> otherwise.
     * @see #isInterrupted()
     * @revised 6.0
     */