对于多线程编程，你理解Java中的synchronized关键字吗？请举例说明。

原创朴灿烈づ我的快乐病毒、 2025-03-23 04:36 55阅读 0赞

`synchronized`关键字是Java中用于实现线程同步的关键字。它主要用于修饰方法或者代码块，以确保在同一时间只有一个线程能够访问被`synchronized`修饰的代码。

以下是一些例子：

1. 修饰方法：
```java
public class Counter {
    private int count = 0;

// synchronized method to increment count
    public synchronized void increment() {
        count++;
    }

// example usage: multiple threads can call increment(), but only one thread at a time
    public static void main(String[] args) {
        Counter counter = new Counter();

Thread thread1 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                counter.increment();
            }
        }));

Thread thread2 = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                counter.increment();
            }
        }));

thread1.start();
        thread2.start();

// wait until both threads finish
        try {
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
```
2. 修饰代码块：
```java
public class PrintCounter {
    private int count = 0;

// synchronized code block to print count
    public synchronized void printCount() {
        System.out.println("Count: " + count);
    }

// example usage: multiple threads can call printCount(), but only one thread at a time
    public static void main(String[] args) {
        PrintCounter counter = new PrintCounter();

Thread thread1 = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                counter.printCount();
            }
        }));

Thread thread2 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                counter.printCount();
            }
        }));

thread1.start();
        thread2.start();

// wait until both threads finish
        try {
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
```
以上例子展示了如何使用`synchronized`关键字来实现线程同步，确保同一时间只有一个线程可以访问共享资源。