在Java中線程間通訊有多種方式，我這里列出一些常用方式，并用代碼的方式展示他們是如何實現(xiàn)的：

共享變量 wait, notify，notifyAll（這3個方法是Object對象中的方法，且必須與synchronized關(guān)鍵字結(jié)合使用） CyclicBarrier、CountDownLatch 利用LockSupport Lock/Condition機制 管道，創(chuàng)建管道輸出流PipedOutputStream和管道輸入流PipedInputStream

示例一：

package com.zhi.test;import java.util.concurrent.CountDownLatch;import java.util.concurrent.atomic.AtomicInteger;import org.junit.Test;/** * Java多線程-線程通訊示例<br> * flag作為共享變量JobB執(zhí)行，notify通知Job執(zhí)行，CountDownLatch通知主線程執(zhí)行 * * @author 張遠志 * @since 2020年5月4日21:51:24 * */public class ThreadTest2 { private CountDownLatch latch; private volatile boolean flag = true; private Object lock = new Object(); private AtomicInteger num = new AtomicInteger(0); class JobA implements Runnable { @Override public void run() { synchronized (lock) {flag = false;if (num.get() != 3) { try { lock.wait(); // wait方法會釋放鎖 } catch (InterruptedException e) { }}System.out.println('任務(wù)A收到通知，繼續(xù)執(zhí)行作業(yè)'); } latch.countDown(); } } class JobB implements Runnable { @Override public void run() { while (flag) { // 保證JobA先申請到鎖 } synchronized (lock) {for (int i = 1; i <= 5; i++) { try { Thread.sleep(1000); } catch (InterruptedException e) { } int a = num.incrementAndGet(); System.out.println('任務(wù)B第' + i + '次執(zhí)行，num值為：' + a); if (a == 3) { lock.notify(); // 喚醒JobB線程，notify方法不會釋放鎖 }} } latch.countDown(); } } @Test public void test() { latch = new CountDownLatch(2); new Thread(new JobA()).start(); new Thread(new JobB()).start(); try { latch.await(); // 保證2個線程都執(zhí)行完畢 } catch (InterruptedException e) { } }}

結(jié)果輸出：

任務(wù)B第1次執(zhí)行，num值為：1任務(wù)B第2次執(zhí)行，num值為：2任務(wù)B第3次執(zhí)行，num值為：3任務(wù)B第4次執(zhí)行，num值為：4任務(wù)B第5次執(zhí)行，num值為：5任務(wù)A收到通知，繼續(xù)執(zhí)行作業(yè)

示例二：

package com.zhi.test;import java.util.concurrent.CountDownLatch;import java.util.concurrent.locks.LockSupport;import org.junit.Test;/** * Java多線程-線程通訊示例，利用LockSupport * * @author 張遠志 * @since 2020年5月4日21:51:24 * */public class ThreadTest3 { private CountDownLatch latch; private volatile int num = 0; private Thread ta; private Thread tb; class JobA implements Runnable { @Override public void run() { if (num != 3) {LockSupport.park(); } System.out.println('任務(wù)A收到通知，繼續(xù)執(zhí)行作業(yè)'); latch.countDown(); } } class JobB implements Runnable { @Override public void run() { for (int i = 1; i <= 5; i++) {try { Thread.sleep(1000);} catch (InterruptedException e) {}num++;System.out.println('任務(wù)B第' + i + '次執(zhí)行，num值為：' + num);if (num == 3) { LockSupport.unpark(ta); // unpark會立即激活傳入線程} } latch.countDown(); } } @Test public void test() { latch = new CountDownLatch(2); ta = new Thread(new JobA()); tb = new Thread(new JobB()); ta.start(); tb.start(); try { latch.await(); // 保證2個線程都執(zhí)行完畢 } catch (InterruptedException e) { } }}

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