Java Thread多線程開(kāi)發(fā)中Object類(lèi)詳細(xì)講解

更新時(shí)間：2023年03月01日 09:55:28 作者：健鑫.

這篇文章主要介紹了Java Thread多線程開(kāi)發(fā)中Object類(lèi)，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)吧

方法概覽

Thread

wait notify notifyAll方法詳解

作用

阻塞階段

使用了wait方法之后，線程就會(huì)進(jìn)入阻塞階段，只有發(fā)生以下四種情況中的其中一個(gè)，線程才會(huì)被喚醒

另一個(gè)線程調(diào)用了這個(gè)線程的notify方法，剛好喚醒的是本線程
另一個(gè)線程調(diào)用了這個(gè)對(duì)象的notifyAll方法
過(guò)了wait規(guī)定的超時(shí)時(shí)間
線程調(diào)用了interrupt

喚醒階段

notify會(huì)喚醒單個(gè)處于阻塞狀態(tài)的線程，喚醒的線程是隨機(jī)的

notify和wait都需要寫(xiě)在synchronized代碼塊里，不然會(huì)拋出異常

notifyAll會(huì)喚醒所有等待的線程

遇到中斷

執(zhí)行wait方法之后，被中斷，會(huì)拋出InterruptedException這個(gè)異常

代碼展示

展示wait和notify的基本用法
該代碼執(zhí)行wait方法之后會(huì)釋放鎖，然后thread2執(zhí)行notify方法
notify方法執(zhí)行完畢之后，并沒(méi)有立即釋放鎖，而是接著執(zhí)行之后的代碼,也就是打印“Thread2調(diào)用notify”這句話
thread2執(zhí)行完畢之后，會(huì)進(jìn)行釋放鎖，thread1才會(huì)繼續(xù)執(zhí)行
在此期間，thread1雖然被喚醒，但是一直在等待thread2同步代碼塊里面的代碼執(zhí)行完畢

public class Wait {
    public static void main(String[] args) throws InterruptedException {
        Thread1 thread1 = new Thread1();
        Thread2 thread2 = new Thread2();
        thread1.start();
        Thread.sleep(200);
        thread2.start();
    }
    public static Object object = new Object();
    static class Thread1 extends Thread {
        @Override
        public void run() {
            synchronized (object) {
                System.out.println("Thread1執(zhí)行");
                try {
                    object.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread1獲取鎖");
            }
        }
    }
    static class Thread2 extends Thread {
        @Override
        public void run() {
            synchronized (object) {
                object.notify();
                System.out.println("Thread2調(diào)用notify");
            }
        }
    }
}
/*
Thread1執(zhí)行
Thread2調(diào)用notify
Thread1獲取鎖
* */

notify和notifyAll的展示
第一個(gè)輸出：threadc調(diào)用notifyAll
第二個(gè)輸出：threadc調(diào)用notify
調(diào)用notify的時(shí)候，程序并沒(méi)有結(jié)束，threadb陷入等待

public class notifyOrAll implements Runnable{
    private static final Object a = new Object();
    public static void main(String[] args) throws InterruptedException {
        Runnable r = new notifyOrAll();
        Thread threada = new Thread(r);
        Thread threadb = new Thread(r);
        Thread threadc = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (a) {
//                    a.notifyAll();
                    a.notify();
                    System.out.println(Thread.currentThread().getName() + "notify");
                }
            }
        });
        threada.start();
        Thread.sleep(200);
        threadb.start();
        Thread.sleep(200);
        threadc.start();
    }
    @Override
    public void run() {
        synchronized (a) {
            System.out.println(Thread.currentThread().getName() + "得到鎖");
            try {
                System.out.println(Thread.currentThread().getName() + "wait");
                a.wait();
                System.out.println(Thread.currentThread().getName() + "wait結(jié)束");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
/*
Thread-0得到鎖
Thread-0wait
Thread-1得到鎖
Thread-1wait
Thread-2notifyAll
Thread-1wait結(jié)束
Thread-0wait結(jié)束
* */
/*
Thread-0得到鎖
Thread-0wait
Thread-1得到鎖
Thread-1wait
Thread-2notify
Thread-0wait結(jié)束
* */

只釋放當(dāng)前monitor
證明wait只釋放當(dāng)前的那把鎖

public class OwnMonitor {
    private static volatile Object a = new Object();
    private static volatile Object b = new Object();
    public static void main(String[] args) throws InterruptedException {
        Thread threadA = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (a) {
                    System.out.println("threadA得到a");
                    synchronized (b) {
                        System.out.println("threadA得到鎖b");

                        try {
                            System.out.println("threadA釋放a");
                            a.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });
        Thread threadB = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (a) {
                    System.out.println("threadB得到a");
                    System.out.println("threadB要獲取b");
                    synchronized (b) {
                        System.out.println("threadB得到b");
                    }
                }
            }
        });
        threadA.start();
        Thread.sleep(1000);
        threadB.start();
    }
}
/*
threadA得到a
threadA得到鎖b
threadA釋放a
threadB得到a
threadB要獲取b
* */

特點(diǎn)

執(zhí)行這些方法必須先獲取鎖
notify只能換取一個(gè)，而且是隨機(jī)的
都屬于Object。任何對(duì)象都可以調(diào)用
都是native final修飾的

當(dāng)線程從wait狀態(tài)剛被喚醒時(shí)，通常不能直接得到鎖，那就會(huì)從waiting狀態(tài)轉(zhuǎn)換到blocked狀態(tài)，搶到鎖之后狀態(tài)轉(zhuǎn)變?yōu)閞unnable

如果發(fā)生異常，則直接跳到Terminated狀態(tài)

通過(guò)wait notify方法實(shí)現(xiàn)生產(chǎn)者和消費(fèi)者

將storge當(dāng)作生產(chǎn)者和消費(fèi)者進(jìn)行工作的倉(cāng)庫(kù)
如果storge中沒(méi)有數(shù)據(jù)，生產(chǎn)者就開(kāi)始wait
如果storge中數(shù)據(jù)滿了，消費(fèi)者就開(kāi)始wait
生產(chǎn)者和消費(fèi)者每進(jìn)行一次生產(chǎn)和消費(fèi)，就執(zhí)行notify

public class ProducerConsumer {
    public static void main(String[] args) {
        Storge storge = new Storge();
        Producer producer = new Producer(storge);
        Consumer consumer = new Consumer(storge);
        new Thread(producer).start();
        new Thread(consumer).start();
    }
}
class Producer implements Runnable {
    private Storge storge;
    public Producer(Storge storge) {
        this.storge = storge;
    }
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            storge.put();
        }
    }
}
class Consumer implements Runnable {
    private Storge storge;
    public Consumer(Storge storge) {
        this.storge = storge;
    }
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            storge.take();
        }
    }
}
class Storge {
    private int maxSize;
    private LinkedList<Date> storge;
    public Storge() {
        maxSize = 10;
        storge = new LinkedList<>();
    }
    public synchronized void put() {
        while (storge.size() == maxSize) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        storge.add(new Date());
        System.out.println("已經(jīng)有了" + storge.size());
        notify();
    }
    public synchronized void take() {
        while (storge.size() == 0) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("拿到了" + storge.poll() + "還剩" + storge.size());
        notify();
    }
}

sleep方法詳解

作用：讓線程在預(yù)期的時(shí)間執(zhí)行，其他時(shí)間不占用CPU資源

特點(diǎn)：和wait不一樣，sleep不釋放鎖

sleep不會(huì)釋放鎖

證明sleep不會(huì)釋放 synchronized鎖

public class SleepSyn implements Runnable{
    public static void main(String[] args) {
        SleepSyn sleepSyn = new SleepSyn();
        new Thread(sleepSyn).start();
        new Thread(sleepSyn).start();
    }
    @Override
    public void run() {
        syn();
    }
    private synchronized void syn() {
        System.out.println(Thread.currentThread().getName() + "獲取鎖");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "釋放鎖");
    }
}
/*
* Thread-0獲取鎖
Thread-0釋放鎖
Thread-1獲取鎖
Thread-1釋放鎖
* */

證明sleep不釋放Lock鎖

public class sleepLock implements Runnable{
    private static final Lock LOCK = new ReentrantLock();
    @Override
    public void run() {
        LOCK.lock();
        System.out.println(Thread.currentThread().getName() + "獲取鎖");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            LOCK.unlock();
        }
        System.out.println(Thread.currentThread().getName() + "釋放鎖");
    }
    public static void main(String[] args) {
        sleepLock sleepLock = new sleepLock();
        new Thread(sleepLock).start();
        new Thread(sleepLock).start();
    }
}
/*
* Thread-0獲取鎖
Thread-0釋放鎖
Thread-1獲取鎖
Thread-1釋放鎖
* */

sleep響應(yīng)中斷

拋出InterruptedException
會(huì)清除中斷狀態(tài)
中斷之后，拋出異常繼續(xù)執(zhí)行

public class sleepInterrupted implements Runnable{
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(new sleepInterrupted());
        thread.start();
        Thread.sleep(2000);
        thread.interrupt();
    }
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(new Date());
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                System.out.println("中斷");
                e.printStackTrace();
            }
        }
    }
}
/*
* Fri Jan 27 21:11:57 CST 2023
Fri Jan 27 21:11:58 CST 2023
中斷
Fri Jan 27 21:11:59 CST 2023
java.lang.InterruptedException: sleep interrupted
   at java.lang.Thread.sleep(Native Method)
   at java.lang.Thread.sleep(Thread.java:340)
   at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
   at com.jx.JavaTest.ThreadObjectMethod.sleepInterrupted.run(sleepInterrupted.java:21)
   at java.lang.Thread.run(Thread.java:748)
Fri Jan 27 21:12:00 CST 2023
Fri Jan 27 21:12:01 CST 2023
Fri Jan 27 21:12:02 CST 2023
Fri Jan 27 21:12:03 CST 2023
Fri Jan 27 21:12:04 CST 2023
Fri Jan 27 21:12:05 CST 2023
Fri Jan 27 21:12:06 CST 2023
Process finished with exit code 0
* */

總結(jié)

sleep方法可以讓線程進(jìn)入waiting狀態(tài)，不占用CPU資源，但是不釋放鎖，規(guī)定時(shí)間之后再運(yùn)行

休眠期間如果被打斷，會(huì)拋出異常并清除中斷狀態(tài)

join方法詳解

新線程加入，主線程等子線程執(zhí)行完畢

代碼展示

前一個(gè)結(jié)果是使用join
后一個(gè)結(jié)果是沒(méi)使用join
可知使用join之后，主線程會(huì)等join的線程執(zhí)行完畢再繼續(xù)執(zhí)行

public class join {
    public static void main(String[] args) throws InterruptedException {
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "執(zhí)行完畢");
            }
        });
        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "執(zhí)行完畢");
            }
        });
        thread1.start();
        thread2.start();
        System.out.println("開(kāi)始等待子線程運(yùn)行");
//        thread1.join();
//        thread2.join();
        System.out.println("所有線程執(zhí)行完畢");
    }
}
/*
* 開(kāi)始等待子線程運(yùn)行
Thread-0執(zhí)行完畢
Thread-1執(zhí)行完畢
所有線程執(zhí)行完畢
* */
/*
* 開(kāi)始等待子線程運(yùn)行
所有線程執(zhí)行完畢
Thread-1執(zhí)行完畢
Thread-0執(zhí)行完畢
* */

遇到中斷
第一個(gè)的運(yùn)行結(jié)果是主線程沒(méi)中斷的打印結(jié)果
第二個(gè)的運(yùn)行結(jié)果是join期間進(jìn)行中斷的打印結(jié)果，可知在打印了“子線程運(yùn)行完畢”之后，依然打印了“啟動(dòng)”兩個(gè)字，可知會(huì)造成運(yùn)行混亂
可以在捕獲異常的代碼塊中，將join的線程也中斷，可以解決上面的問(wèn)題

public class joinInterrupt {
    public static void main(String[] args) {
        Thread main1 = Thread.currentThread();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    main1.interrupt();
                    Thread.sleep(2000);
                    System.out.println("啟動(dòng)");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        thread1.start();
        System.out.println("join");
        try {
            thread1.join();
        } catch (InterruptedException e) {
            System.out.println(Thread.currentThread().getName() + "中斷");
            // thread1.interrupt();
            e.printStackTrace();
        }
        System.out.println("子線程運(yùn)行完畢");
    }
}
/*
* join
啟動(dòng)
子線程運(yùn)行完畢
* */
/*
* join
main中斷
子線程運(yùn)行完畢
java.lang.InterruptedException
   at java.lang.Object.wait(Native Method)
   at java.lang.Thread.join(Thread.java:1252)
   at java.lang.Thread.join(Thread.java:1326)
   at com.jx.JavaTest.ThreadObjectMethod.joinInterrupt.main(joinInterrupt.java:23)
啟動(dòng)
Process finished with exit code 0
* */
/*
* join
main中斷
子線程運(yùn)行完畢
java.lang.InterruptedException: sleep interrupted
   at java.lang.Thread.sleep(Native Method)
   at com.jx.JavaTest.ThreadObjectMethod.joinInterrupt$1.run(joinInterrupt.java:13)
   at java.lang.Thread.run(Thread.java:748)
java.lang.InterruptedException
   at java.lang.Object.wait(Native Method)
   at java.lang.Thread.join(Thread.java:1252)
   at java.lang.Thread.join(Thread.java:1326)
   at com.jx.JavaTest.ThreadObjectMethod.joinInterrupt.main(joinInterrupt.java:23)
Process finished with exit code 0
* */

join期間，線程處于WAITING狀態(tài)

public class joinStates {
    public static void main(String[] args) throws InterruptedException {
        Thread main1 = Thread.currentThread();
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(3000);
                    System.out.println(main1.getState());
                    System.out.println("子線程運(yùn)行結(jié)束");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        thread.start();
        System.out.println("join");
        thread.join();
        System.out.println("運(yùn)行完畢");
    }
}
/*
* join
WAITING
子線程運(yùn)行結(jié)束
運(yùn)行完畢
* */

yield方法

用來(lái)釋放CPU時(shí)間片，但是不一定能達(dá)到預(yù)期的效果，因?yàn)橛袝r(shí)CPU資源不緊張，無(wú)需yield

和sleep的區(qū)別是：sleep期間不會(huì)被再次調(diào)度但是yield會(huì)立刻處于競(jìng)爭(zhēng)狀態(tài)，還會(huì)隨時(shí)再次被調(diào)度

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