不同锁机制对 Java 多线程函数失效的性能差异？

import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class LockPerformanceTest {

    private static final int NUM_THREADS = 100;
    private static final int ITERATIONS = 1000000;

    private static int counter;
    private static Object lock = new Object();
    private static ReentrantLock reentrantLock = new ReentrantLock();
    private static ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    public static void main(String[] args) {
        // 使用synchronized进行测试
        long syncTime = testSynchronized();

        // 使用ReentrantLock进行测试
        long lockTime = testReentrantLock();

        // 使用ReadWriteLock进行测试
        long rwTime = testReadWriteLock();

        System.out.println("Synchronized: " + syncTime + " ms");
        System.out.println("ReentrantLock: " + lockTime + " ms");
        System.out.println("ReadWriteLock: " + rwTime + " ms");
    }

    private static long testSynchronized() {
        Thread[] threads = new Thread[NUM_THREADS];
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < NUM_THREADS; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < ITERATIONS; j++) {
                    synchronized (lock) {
                        counter++;
                    }
                }
            });
        }

        for (Thread thread : threads) {
            thread.start();
        }

        for (Thread thread : threads) {
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long endTime = System.currentTimeMillis();
        return endTime - startTime;
    }

    private static long testReentrantLock() {
        Thread[] threads = new Thread[NUM_THREADS];
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < NUM_THREADS; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < ITERATIONS; j++) {
                    reentrantLock.lock();
                    try {
                        counter++;
                    } finally {
                        reentrantLock.unlock();
                    }
                }
            });
        }

        for (Thread thread : threads) {
            thread.start();
        }

        for (Thread thread : threads) {
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long endTime = System.currentTimeMillis();
        return endTime - startTime;
    }

    private static long testReadWriteLock() {
        Thread[] threads = new Thread[NUM_THREADS];
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < NUM_THREADS; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < ITERATIONS; j++) {
                    // 大多数线程进行读操作
                    readWriteLock.readLock().lock();
                    try {
                        counter++;
                    } finally {
                        readWriteLock.readLock().unlock();
                    }
                }
            });
        }

        for (Thread thread : threads) {
            thread.start();
        }

        for (Thread thread : threads) {
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long endTime = System.currentTimeMillis();
        return endTime - startTime;
    }
}

Synchronized: 3124 ms
ReentrantLock: 2215 ms
ReadWriteLock: 1345 ms