How to handle concurrent access to objects in Java?

Abstract: Java provides a variety of concurrent access mechanisms to solve the problem of concurrent access to objects: Synchronized blocks and methods: Using the synchronized keyword, only one thread is allowed to access a code block or method at a time. Lock: Create a lock object and use synchronized to synchronize its access. Atomic variables: Use atomic variables such as Java's AtomicInteger to achieve thread-safe reading and writing of basic types.

Concurrent access to objects in Java: processing methods and practical cases

Concurrent access issues

When multiple threads access the same object at the same time objects, this may cause concurrency issues such as data inconsistency or deadlocks. This is common in multi-threaded environments and can lead to errors that are difficult to debug if not handled properly.

Methods to handle concurrent access

Java provides a variety of mechanisms to handle concurrent access to objects:

• Synchronized blocks and methods: Use the synchronized keyword to make a code block or method accessible only by one thread at a time.
• Lock: Create a lock object and synchronize its access using synchronized.
• Atomic variables: Use Java's AtomicInteger and other atomic variables to achieve thread-safe reading and writing of basic types.

Practical case

Sync block:

// 实例变量 num 受保护
private int num;

public void increment() {
    synchronized (this) {
        num++;
    }
}

Lock:

// 创建锁对象
private final Object lock = new Object();

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

Atomic variables:

// num 是一个 AtomicInteger，保证线程安全
private AtomicInteger num = new AtomicInteger(0);

public void increment() {
    num.incrementAndGet();
}

Select method

Which method to choose depends on the specific scenario:

• Synchronized blocks and methods: Simple and easy to use, but may cause performance degradation.
• Lock: More flexible, performance is slightly better than synchronized block.
• Atomic variables: Suitable for basic types and have the best performance.

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