Introduction to the usage of counterexamples and positive examples of Java ReentrantLock

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Release lock in finally

When using ReentrantLock, you must remember to release the lock, otherwise it will cause the lock to be occupied all the time, and other threads that use the lock will wait forever, so when we use ReentrantLock, we must release the lock in finally, so that we can ensure that the lock will be released.

counterexample

import java.util.concurrent.locks.ReentrantLock; publicclass LockExample { //Create lock object privatestaticfinal ReentrantLock lock = new ReentrantLock(); public static void main(String[] args) { //lock operation lock.lock(); System.out.println("Hello,ReentrantLock. "); //exception will be reported here, causing the lock not to be released properly int number = 1 / 0; //release lock lock.unlock(); System.out.println("Lock released successfully! "); }}

When an exception occurs and the lock is not released properly, other threads that use the lock are left in a permanent wait state.

positive examples

import java.util.concurrent.locks.ReentrantLock; publicclass LockExample { //Create lock object privatestaticfinal ReentrantLock lock = new ReentrantLock(); public static void main(String[] args) { //lock operation lock.lock(); try { System.out.println("Hello,ReentrantLock. "); //exception will be reported here int number = 1 / 0; } finally { //release lock lock.unlock(); System.out.println("Lock released successfully! "); } }}

Although an exception occurs in the method, it does not affect the release of the ReentrantLock lock, so that other threads using this lock can acquire and run normally.

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