Java多线程编程与并发控制策略

Java多线程编程与并发控制策略

大家好，我是免费搭建查券返利机器人省钱赚佣金就用微赚淘客系统3.0的小编，也是冬天不穿秋裤，天冷也要风度的程序猿！今天，我想和大家分享一下Java多线程编程与并发控制策略的相关知识，希望对大家有所帮助。

一、Java多线程编程基础

1.1 线程的创建与启动

在Java中，线程可以通过继承Thread类或实现Runnable接口来创建和启动。

// 继承Thread类
class MyThread extends Thread {public void run() {System.out.println("Thread is running");}
}// 实现Runnable接口
class MyRunnable implements Runnable {public void run() {System.out.println("Runnable is running");}
}public class Main {public static void main(String[] args) {MyThread thread1 = new MyThread();thread1.start();Thread thread2 = new Thread(new MyRunnable());thread2.start();}
}

1.2 线程的生命周期

线程在Java中的生命周期包括以下几个阶段：

新建（New）：线程对象被创建，但尚未调用start()方法。
就绪（Runnable）：start()方法被调用，线程进入就绪状态，等待CPU调度。
运行（Running）：线程获得CPU资源，开始执行run()方法。
阻塞（Blocked）：线程因某些原因（如等待I/O操作）进入阻塞状态。
终止（Terminated）：线程执行完run()方法或因异常退出。

二、并发控制策略

2.1 同步（Synchronized）

Synchronized关键字用于保证多个线程访问共享资源时的互斥性，防止数据不一致问题。

class Counter {private int count = 0;public synchronized void increment() {count++;}public synchronized int getCount() {return count;}
}public class Main {public static void main(String[] args) {Counter counter = new Counter();Thread t1 = new Thread(() -> {for (int i = 0; i < 1000; i++) {counter.increment();}});Thread t2 = new Thread(() -> {for (int i = 0; i < 1000; i++) {counter.increment();}});t1.start();t2.start();try {t1.join();t2.join();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Count: " + counter.getCount());}
}

2.2 显式锁（Explicit Lock）

ReentrantLock是Java中的显式锁，提供了比Synchronized更灵活的锁机制。

import java.util.concurrent.locks.ReentrantLock;class Counter {private int count = 0;private final ReentrantLock lock = new ReentrantLock();public void increment() {lock.lock();try {count++;} finally {lock.unlock();}}public int getCount() {lock.lock();try {return count;} finally {lock.unlock();}}
}

2.3 信号量（Semaphore）

Semaphore用于控制同时访问某个特定资源的线程数量。

import java.util.concurrent.Semaphore;class Resource {private final Semaphore semaphore = new Semaphore(3);public void use() {try {semaphore.acquire();System.out.println("Resource in use by " + Thread.currentThread().getName());Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();} finally {semaphore.release();}}
}public class Main {public static void main(String[] args) {Resource resource = new Resource();for (int i = 0; i < 10; i++) {new Thread(resource::use).start();}}
}

2.4 读写锁（ReadWriteLock）

ReadWriteLock允许多个读操作同时进行，但写操作独占。

import java.util.concurrent.locks.ReentrantReadWriteLock;class SharedData {private int data = 0;private final ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();public void write(int value) {rwLock.writeLock().lock();try {data = value;} finally {rwLock.writeLock().unlock();}}public int read() {rwLock.readLock().lock();try {return data;} finally {rwLock.readLock().unlock();}}
}

三、并发工具类

3.1 CountDownLatch

CountDownLatch用于让一个或多个线程等待其他线程完成操作。

import java.util.concurrent.CountDownLatch;public class Main {public static void main(String[] args) {CountDownLatch latch = new CountDownLatch(3);for (int i = 0; i < 3; i++) {new Thread(() -> {System.out.println(Thread.currentThread().getName() + " is working");latch.countDown();}).start();}try {latch.await();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("All threads have finished");}
}

3.2 CyclicBarrier

CyclicBarrier用于让一组线程等待至某个状态，然后同时执行。

import java.util.concurrent.CyclicBarrier;public class Main {public static void main(String[] args) {CyclicBarrier barrier = new CyclicBarrier(3, () -> System.out.println("All threads have reached the barrier"));for (int i = 0; i < 3; i++) {new Thread(() -> {System.out.println(Thread.currentThread().getName() + " is working");try {barrier.await();} catch (Exception e) {e.printStackTrace();}}).start();}}
}