78-java 多线程如何共享数据
在Java中,多个线程可以通过共享对象来共享数据。这可以通过以下几种方式实现:
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实例变量共享:如果多个线程访问同一个对象的实例变量,那么这些线程将共享这些实例变量。
public class SharedData {public int sharedData = 0;public void increase() {sharedData++;} }public class ThreadExample implements Runnable {private SharedData sharedData;public ThreadExample(SharedData sharedData) {this.sharedData = sharedData;}@Overridepublic void run() {for (int i = 0; i < 10; i++) {sharedData.increase();}} }public class Main {public static void main(String[] args) {SharedData sharedData = new SharedData();ThreadExample example = new ThreadExample(sharedData);Thread t1 = new Thread(example);Thread t2 = new Thread(example);t1.start();t2.start();try {t1.join();t2.join();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("SharedData: " + sharedData.sharedData);} }
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使用
volatile
关键字:如果你希望确保所有线程看到共享变量的最新值,并且不会缓存这个变量的旧值,你可以使用volatile
关键字。public class SharedData {public volatile int sharedData = 0;public void increase() {sharedData++;} }
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使用
synchronized
关键字:当你需要在多个线程之间同步访问共享数据时,可以使用synchronized
关键字。public class SharedData {public int sharedData = 0;public synchronized void increase() {sharedData++;} }
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使用
ReentrantLock
:ReentrantLock
提供了比synchronized
更广泛的锁定操作,可以更灵活地控制同步。import java.util.concurrent.locks.ReentrantLock;public class SharedData {public int sharedData = 0;private final ReentrantLock lock = new ReentrantLock();public void increase() {lock.lock();try {sharedData++;} finally {lock.unlock();}} }
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使用原子变量:
java.util.concurrent.atomic
包中的原子变量类提供了一种方式来进行无锁的、线程安全的操作。import java.util.concurrent.atomic.AtomicInteger;public class SharedData {public AtomicInteger sharedData = new AtomicInteger(0);public void increase() {sharedData.incrementAndGet();} }
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使用线程安全集合:
java.util.concurrent
包中提供了一些线程安全的集合类,可以用来存储共享数据。import java.util.concurrent.ConcurrentHashMap;public class SharedData {public ConcurrentHashMap<String, Integer> sharedData = new ConcurrentHashMap<>();public void increase(String key) {sharedData.compute(key, (k, v) -> v == null ? 1 : v + 1);} }
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使用
ThreadLocal
:ThreadLocal
可以为每个线程提供一个独立的变量副本,从而避免共享数据。public class ThreadLocalExample {public static final ThreadLocal<Integer> localData =