How can we avoid deadlock in Java?-javaTutorial-php.cn

How can we avoid deadlock in Java?

In Java,Deadlockis a programming situation in whichtwo or more threads are permanently blocked. A deadlock condition will occur between at leasttwo threadsandtwo or more resources.

How to avoid deadlock

Avoid nested locks: Deadlock mainly occurs when locks are provided to multiple threads. If we have already provided a lock to one thread, avoid providing locks to other threads.
Avoid unnecessary locks: We only need to provide locks to those necessary members. Providing locks unnecessarily can lead to deadlocks.
Use Thread.join(): A deadlock condition occurs when one thread is waiting for another thread to complete. If this happens, we can useThread.join()and set the maximum execution time.

Example

public class DeadlockTest { public static void main(String[] args) throws InterruptedException { Object obj1 = new Object(); Object obj2 = new Object(); Object obj3 = new Object(); Thread t1 = new Thread(new SyncThread(obj1, obj2), "t1"); Thread t2 = new Thread(new SyncThread(obj2, obj3), "t2"); t1.start(); Thread.sleep(2000); t2.start(); Thread.sleep(2000); } } class SyncThread implements Runnable { private Object obj1; private Object obj2; public SyncThread(Object o1, Object o2){ this.obj1=o1; this.obj2=o2; } @Override public void run() { String name = Thread.currentThread().getName(); System.out.println(name + " acquiring lock on " + obj1); synchronized (obj1) { System.out.println(name + " acquired lock on " + obj1); work(); } System.out.println(name + " released lock on " + obj1); System.out.println(name + " acquiring lock on " + obj2); synchronized (obj2) { System.out.println(name + " acquired lock on " + obj2); work(); } System.out.println(name + " released lock on " + obj2); System.out.println(name + " finished execution."); } private void work() { try { Thread.sleep(5000); } catch (InterruptedException ie) { ie.printStackTrace(); } } }

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Output

t1 acquiring lock on java.lang.Object@917d8d4 t1 acquired lock on java.lang.Object@917d8d4 t2 acquiring lock on java.lang.Object@5c4b42fb t2 acquired lock on java.lang.Object@5c4b42fb t1 released lock on java.lang.Object@917d8d4 t1 acquiring lock on java.lang.Object@5c4b42fb t1 acquired lock on java.lang.Object@5c4b42fb t2 released lock on java.lang.Object@5c4b42fb t2 acquiring lock on java.lang.Object@528cb702 t2 acquired lock on java.lang.Object@528cb702 t1 released lock on java.lang.Object@5c4b42fb t2 released lock on java.lang.Object@528cb702 t1 finished execution. t2 finished execution.

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