How to solve thread synchronization and resource contention issues in Java

How to solve the problem of thread synchronization and resource competition in Java

In multi-threaded concurrent programming, thread synchronization and resource competition are common problems. To ensure correct cooperation between threads, we need to use appropriate synchronization mechanisms to solve these problems. In Java, some mechanisms are provided to achieve thread synchronization, the most commonly used of which is to use the synchronized keyword and lock to achieve synchronization.

1. Use the synchronized keyword

The synchronized keyword can be used to modify methods or code blocks to achieve mutually exclusive access to resources. When a thread enters a synchronized code block, it acquires a lock and other threads are blocked until the lock is released.

Example 1: Using synchronized modification method

public class SyncExample {
  private int count = 0;

  public synchronized void increment() {
    count++;
  }

  public synchronized int getCount() {
    return count;
  }
}

In the above example, both the increment() and getCount() methods are modified with the synchronized keyword to ensure atomic operations on the count variable. . In this way, when multiple threads call the increment() method or getCount() method at the same time, they will be executed in order, avoiding data inconsistency.

Example 2: Using synchronized to modify the code block

public class SyncExample {
  private int count = 0;
  private Object lock = new Object();

  public void increment() {
    synchronized (lock) {
      count++;
    }
  }

  public int getCount() {
    synchronized (lock) {
      return count;
    }
  }
}

In the above example, access to the count variable is wrapped in the synchronized code block, and mutual interaction is achieved by passing in the same lock object lock. Deny access. This method is more flexible than using the synchronized modification method and can control the granularity of the lock.

2. Using ReentrantLock

In addition to using the synchronized keyword, Java also provides the ReentrantLock class to implement thread synchronization. ReentrantLock provides more functions, such as interruptible, time-limited, etc., making it more flexible.

Example:

public class LockExample {
  private int count = 0;
  private Lock 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 example, the resource is locked through lock(), and then unlock() is used in the finally block to release the lock. ReentrantLock ensures mutually exclusive access to resources and allows for more flexibility.

It should be noted that when using synchronized or ReentrantLock to achieve thread synchronization, make sure that all threads use the same lock object, otherwise synchronization cannot be achieved.

Summary:

In multi-threaded concurrent programming, thread synchronization and resource competition are common problems. To solve this problem, you can use the synchronized keyword or ReentrantLock to achieve thread synchronization. When using synchronized, you can modify methods or code blocks; when using ReentrantLock, you need to manually call the lock() and unlock() methods to lock and unlock. No matter which method is used, you need to ensure that all threads use the same lock object to achieve correct synchronization.

The above are some methods and sample codes on how to solve thread synchronization and resource competition problems in Java. In actual programming, it is very important to choose the appropriate synchronization mechanism according to specific needs and scenarios.

The above is the detailed content of How to solve thread synchronization and resource contention issues in Java. For more information, please follow other related articles on the PHP Chinese website!