目錄

• 在子線程中通過join()方法指定順序
• 在主線程中通過join()方法指定順序
• 通過倒數(shù)計時器CountDownLatch實現(xiàn)
• 通過創(chuàng)建單一化線程池newSingleThreadExecutor()實現(xiàn)

在子線程中通過join()方法指定順序

通過join()方法使當(dāng)前線程“阻塞”，等待指定線程執(zhí)行完畢后繼續(xù)執(zhí)行。JA128資訊網(wǎng)——每日最新資訊28at.com

舉例：在線程thread2中，加上一句thread1.join()，其意義在于，當(dāng)前線程2運行到此行代碼時會進入阻塞狀態(tài)，直到線程thread1執(zhí)行完畢后，線程thread2才會繼續(xù)運行，這就保證了線程thread1與線程thread2的運行順序。JA128資訊網(wǎng)——每日最新資訊28at.com

public class ThreadJoinDemo {    public static void main(String[] args) throws InterruptedException {        final Thread thread1 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("打開冰箱！");            }        });         final Thread thread2 = new Thread(new Runnable() {            @Override            public void run() {                try {                    thread1.join();                } catch (InterruptedException e) {                    e.printStackTrace();                }                System.out.println("拿出一瓶牛奶！");            }        });         final Thread thread3 = new Thread(new Runnable() {            @Override            public void run() {                try {                    thread2.join();                } catch (InterruptedException e) {                    e.printStackTrace();                }                System.out.println("關(guān)上冰箱！");            }        });         //下面三行代碼順序可隨意調(diào)整，程序運行結(jié)果不受影響，因為我們在子線程中通過“join()方法”已經(jīng)指定了運行順序。        thread3.start();        thread2.start();        thread1.start();     }}

運行結(jié)果：JA128資訊網(wǎng)——每日最新資訊28at.com

打開冰箱！拿出一瓶牛奶！關(guān)上冰箱！

在主線程中通過join()方法指定順序

簡單說一下子線程與主線程的區(qū)別，子線程指的是發(fā)生在Thread內(nèi)部的代碼，主線程指的是發(fā)生在main函數(shù)中的代碼，我們可以在main函數(shù)中通過join()方法讓主線程阻塞等待以達到指定順序執(zhí)行的目的。JA128資訊網(wǎng)——每日最新資訊28at.com

public class ThreadMainJoinDemo {    public static void main(String[] args) throws InterruptedException {        final Thread thread1 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("打開冰箱！");            }        });         final Thread thread2 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("拿出一瓶牛奶！");            }        });         final Thread thread3 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("關(guān)上冰箱！");            }        });         thread1.start();        thread1.join();        thread2.start();        thread2.join();        thread3.start();    }}

輸出結(jié)果：JA128資訊網(wǎng)——每日最新資訊28at.com

打開冰箱！拿出一瓶牛奶！關(guān)上冰箱！

通過倒數(shù)計時器CountDownLatch實現(xiàn)

CountDownLatch通過計數(shù)器提供了更靈活的控制，只要檢測到計數(shù)器為0當(dāng)前線程就可以往下執(zhí)行而不用管相應(yīng)的thread是否執(zhí)行完畢。JA128資訊網(wǎng)——每日最新資訊28at.com

public class ThreadCountDownLatchDemo {     private static CountDownLatch countDownLatch1 = new CountDownLatch(1);     private static CountDownLatch countDownLatch2 = new CountDownLatch(1);     public static void main(String[] args) {        final Thread thread1 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("打開冰箱！");                countDownLatch1.countDown();            }        });         final Thread thread2 = new Thread(new Runnable() {            @Override            public void run() {                try {                    countDownLatch1.await();                    System.out.println("拿出一瓶牛奶！");                    countDownLatch2.countDown();                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        });         final Thread thread3 = new Thread(new Runnable() {            @Override            public void run() {                try {                    countDownLatch2.await();                    System.out.println("關(guān)上冰箱！");                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        });         //下面三行代碼順序可隨意調(diào)整，程序運行結(jié)果不受影響        thread3.start();        thread1.start();        thread2.start();    }}

輸出結(jié)果：JA128資訊網(wǎng)——每日最新資訊28at.com

打開冰箱！拿出一瓶牛奶！關(guān)上冰箱！

通過創(chuàng)建單一化線程池newSingleThreadExecutor()實現(xiàn)

單線程化線程池(newSingleThreadExecutor)的優(yōu)點，串行執(zhí)行所有任務(wù)。JA128資訊網(wǎng)——每日最新資訊28at.com

public class ThreadPoolDemo {    static ExecutorService executorService = Executors.newSingleThreadExecutor();     public static void main(String[] args) {        final Thread thread1 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("打開冰箱！");            }        });         final Thread thread2 =new Thread(new Runnable() {            @Override            public void run() {                System.out.println("拿出一瓶牛奶！");            }        });         final Thread thread3 = new Thread(new Runnable() {            @Override            public void run() {                System.out.println("關(guān)上冰箱！");            }        });        executorService.submit(thread1);        executorService.submit(thread2);        executorService.submit(thread3);        executorService.shutdown();        //使用完畢記得關(guān)閉線程池    }}

輸出結(jié)果：JA128資訊網(wǎng)——每日最新資訊28at.com

打開冰箱！拿出一瓶牛奶！關(guān)上冰箱！

JA128資訊網(wǎng)——每日最新資訊28at.com

本文鏈接：http://www.www897cc.com/showinfo-26-96998-0.html掌握這四種方法，多線程按序執(zhí)行不再是問題

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