Java Thread多線程開發(fā)中Object類詳細講解

更新時間：2023年03月01日 09:55:28 作者：健鑫.

這篇文章主要介紹了Java Thread多線程開發(fā)中Object類，文中通過示例代碼介紹的非常詳細，對大家的學習或者工作具有一定的參考學習價值，需要的朋友們下面隨著小編來一起學習吧

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，線程就會進入阻塞階段，只有發(fā)生以下四種情況中的其中一個，線程才會被喚醒

另一個線程調(diào)用了這個線程的notify方法，剛好喚醒的是本線程
另一個線程調(diào)用了這個對象的notifyAll方法
過了wait規(guī)定的超時時間
線程調(diào)用了interrupt

喚醒階段

notify會喚醒單個處于阻塞狀態(tài)的線程，喚醒的線程是隨機的

notify和wait都需要寫在synchronized代碼塊里，不然會拋出異常

notifyAll會喚醒所有等待的線程

遇到中斷

執(zhí)行wait方法之后，被中斷，會拋出InterruptedException這個異常

代碼展示

展示wait和notify的基本用法
該代碼執(zhí)行wait方法之后會釋放鎖，然后thread2執(zhí)行notify方法
notify方法執(zhí)行完畢之后，并沒有立即釋放鎖，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，會進行釋放鎖，thread1才會繼續(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
第一個輸出：threadc調(diào)用notifyAll
第二個輸出：threadc調(diào)用notify
調(diào)用notify的時候，程序并沒有結(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
* */

只釋放當前monitor
證明wait只釋放當前的那把鎖

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

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

當線程從wait狀態(tài)剛被喚醒時，通常不能直接得到鎖，那就會從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wait notify方法實現(xiàn)生產(chǎn)者和消費者

將storge當作生產(chǎn)者和消費者進行工作的倉庫
如果storge中沒有數(shù)據(jù)，生產(chǎn)者就開始wait
如果storge中數(shù)據(jù)滿了，消費者就開始wait
生產(chǎn)者和消費者每進行一次生產(chǎn)和消費，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)期的時間執(zhí)行，其他時間不占用CPU資源

特點：和wait不一樣，sleep不釋放鎖

sleep不會釋放鎖

證明sleep不會釋放 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方法可以讓線程進入waiting狀態(tài)，不占用CPU資源，但是不釋放鎖，規(guī)定時間之后再運行

休眠期間如果被打斷，會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

前一個結(jié)果是使用join
后一個結(jié)果是沒使用join
可知使用join之后，主線程會等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("開始等待子線程運行");
//        thread1.join();
//        thread2.join();
        System.out.println("所有線程執(zhí)行完畢");
    }
}
/*
* 開始等待子線程運行
Thread-0執(zhí)行完畢
Thread-1執(zhí)行完畢
所有線程執(zhí)行完畢
* */
/*
* 開始等待子線程運行
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
第一個的運行結(jié)果是主線程沒中斷的打印結(jié)果
第二個的運行結(jié)果是join期間進行中斷的打印結(jié)果，可知在打印了“子線程運行完畢”之后，依然打印了“啟動”兩個字，可知會造成運行混亂
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");
                } 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("子線程運行完畢");
    }
}
/*
* join
啟動
子線程運行完畢
* */
/*
* join
main中斷
子線程運行完畢
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
Process finished with exit code 0
* */
/*
* join
main中斷
子線程運行完畢
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("子線程運行結(jié)束");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        thread.start();
        System.out.println("join");
        thread.join();
        System.out.println("運行完畢");
    }
}
/*
* join
WAITING
子線程運行結(jié)束
運行完畢
* */