How to solve concurrency race issues in Java

How to solve the problem of concurrency competition in Java requires specific code examples

Introduction: In multi-thread programming, a problem we often encounter is concurrency competition. . When multiple threads access shared resources at the same time, data inconsistency or deadlock may occur. In Java, some mechanisms and tools are provided to solve these problems. This article will introduce in detail how to solve the concurrency competition problem in Java and give specific code examples.

1. Use the synchronized keyword

The synchronized keyword is one of the most basic methods provided by Java to solve the problem of concurrency competition. The synchronized keyword can be used to mark a method or code block as synchronized. Only one thread can access the method or code block at the same time, and other threads need to wait.

Code example:

public class Example {
    private int count = 0;
    
    public synchronized void increment() {
        count++;
    }
    
    public synchronized int getCount() {
        return count;
    }
}

In the above code, the increment() method and getCount() method are marked as synchronized, ensuring that only one thread can access these two at the same time. method. This solves the problem of concurrency competition.

2. Use the ReentrantLock class

In addition to using the synchronized keyword, Java also provides the ReentrantLock class to resolve concurrency competition. The ReentrantLock class is a reentrant mutex lock that can replace the synchronized keyword to synchronize access to shared resources.

Code example:

import java.util.concurrent.locks.ReentrantLock;

public class Example {
    private int count = 0;
    private ReentrantLock lock = new ReentrantLock();
    
    public void increment() {
        lock.lock();
        try {
            count++;
        } finally {
            lock.unlock();
        }
    }
    
    public int getCount() {
        lock.lock();
        try {
            return count;
        } finally {
            lock.unlock();
        }
    }
}

In the above code, use the ReentrantLock class to achieve synchronous access to count. In the increment() method and getCount() method, the lock is acquired and released by calling the lock() method and unlock() method. This ensures that only one thread can access these methods at the same time, solving the problem of concurrency competition.

3. Use Atomic classes

In addition to using locks to achieve synchronous access to shared resources, Java also provides some atomic classes, such as AtomicInteger, AtomicLong, etc., which can directly operate the underlying memory , implement atomic operations on shared resources and avoid race conditions.

Code example:

import java.util.concurrent.atomic.AtomicInteger;

public class Example {
    private AtomicInteger count = new AtomicInteger(0);
    
    public void increment() {
        count.incrementAndGet();
    }
    
    public int getCount() {
        return count.get();
    }
}

In the above code, use the AtomicInteger class to replace the int type count, and atomically increase and get the count through the incrementAndGet() method and get() method value. This avoids race conditions and solves the problem of concurrency competition.

Summary: In Java, we can use the synchronized keyword, ReentrantLock class and Atomic class to solve the problem of concurrency competition. The specific choice depends on the actual needs and scenarios. This article gives specific code examples, hoping to help readers better understand and solve concurrency competition problems in Java.

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