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

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

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：

修饰方法：

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();
     }
 }
}

修饰代码块：

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();
     }
 }
}