Java笔记杨枝12.3

Java等待唤醒机制

package prc02;public class StudentDemo {    public static void main(String[] args) {        Student s = new Student();        SetThread st = new SetThread(s);        GetThread gt = new GetThread(s);        Thread t1 = new Thread(st, "a");        Thread t2 = new Thread(gt, "b");        t1.start();        t2.start();    }}//学生类public class Student {    String name;    int age ;    //声明一个变量    boolean flag ; //默认没有数据,如果true,则说明有数据}//消费者public class GetThread implements Runnable {    private Student s;    public GetThread(Student s) {        this.s = s;    }    public void run() {        while (true) {            synchronized (s) {                if (!s.flag) {                    try {                        s.wait();                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                }                System.out.println(s.name + "---" + s.age);                // 修改标记                s.flag = false;// 消费者线程                // 通知对方(t1线程),消费者线程没有数据类,赶紧来消费                s.notify();// 唤醒t1线程....            }        }    }}//生产者package prc02;public class SetThread implements Runnable {    private Student s;    // 用构造函数使得他们用的都是同一个对象资源    public SetThread(Student s) {        this.s = s;    }    private int x = 0;    public void run() {        while (true) {            synchronized (s) {                if (s.flag) {                    try {                        s.wait();                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                }                if (x % 2 == 0) {                    // 设置学生数据                    s.name = "杨枝";                    s.age = 24;                } else {                    s.name = "小明";                    s.age = 12;                }                x++;                // 修改标记                s.flag = true;// 有数据了                // 通知t2:消费者线程来消费数据                s.notify();// 唤醒等待这种状态...            }        }    }}

线程组
public ThreadGroup(String name)构造一个新线程组
public Thread(ThreadGroup group,Runnable target ,String name)

package prac03;public class Prac03 {public static void main(String[] args) {    //method1();    method2();}private static void method2() {    ThreadGroup tg = new ThreadGroup("这是一个新的线程组") ;    //public Thread(ThreadGroup group,Runnable target ,String name){}    MyRunnable my = new MyRunnable() ;    Thread t1 = new Thread(tg, my, "线程1") ;    Thread t2 = new Thread(tg, my, "线程2") ;    ThreadGroup tg1 = t1.getThreadGroup() ;    ThreadGroup tg2 = t2.getThreadGroup() ;    System.out.println(tg1.getName());    System.out.println(tg2.getName());    System.out.println(Thread.currentThread().getThreadGroup().getName());    tg.setDaemon(true) ;}private static void method1() {    MyRunnable my = new MyRunnable() ;    Thread t1 = new Thread(my) ;    Thread t2 = new Thread(my) ;    //public final ThreadGroup getThreadGroup()返回该线程所属的线程组    ThreadGroup tg1 = t1.getThreadGroup() ;    ThreadGroup tg2 = t2.getThreadGroup() ;    String name1 = tg1.getName() ;    String name2 = tg2.getName() ;    ////子线程默认的线程组名称:main线程    System.out.println(name1);    System.out.println(name2);    System.out.println(Thread.currentThread().getThreadGroup().getName());    t1.start() ;    t2.start() ;}}public class MyRunnable implements Runnable {    @Override    public void run() {        for(int x = 0 ; x <100 ; x ++){            System.out.println(Thread.currentThread().getName()+":"+x);        }    }}

最终版生产者-消费者模式
将学生类成员变量私有化
提供两个同步方法
两个线程可以直接调用

public class StudentDemo {    public static void main(String[] args) {        Student s = new Student();        SetThread st = new SetThread(s);        GetThread gt = new GetThread(s);        Thread t1 = new Thread(st, "a");        Thread t2 = new Thread(gt, "b");        t1.start();        t2.start();    }}//学生类public class Student {    private String name;    private int age;    private boolean flag; // 默认没有数据,如果true,则说明有数据    public synchronized void set(String name, int age) {        if (this.flag) {            try {                this.wait();            } catch (InterruptedException e) {                e.printStackTrace();            }        }        this.name = name;        this.age = age;        // 修改标记        this.flag = true;// 有数据了        // 通知t2:消费者线程来消费数据        this.notify();// 唤醒等待这种状态...    }    public synchronized void get() {        if (!this.flag) {            try {                this.wait();// 调用的时候,会立即释放锁            } catch (InterruptedException e) {                e.printStackTrace();            }        }        System.out.println(this.name + "---" + this.age);        // 修改标记        this.flag = false;        this.notify();// 唤醒t1线程....    }}//消费者public class GetThread implements Runnable {    private Student s;    public GetThread(Student s) {        this.s = s;    }    public void run() {        while (true) {            s.get();        }    }}//生产者public class SetThread implements Runnable {    private Student s;    // 用构造函数使得他们用的都是同一个对象资源    public SetThread(Student s) {        this.s = s;    }    private int x = 0;    public void run() {        while (true) {            if (x % 2 == 0) {                s.set("小王", 32);            } else {                s.set("小明", 22);            }            x++;        }    }}

线程池
很多子线程调用完毕不会立即被回收掉,而是会回到线程池中被多次利用（节约成本）

public class MyRunnable implements Runnable {    @Override    public void run() {        //for循环        for(int x = 0 ; x < 100 ; x ++){            System.out.println(Thread.currentThread().getName()+":"+x);        }    }}//测试类public class ExecutorsDemo {    public static void main(String[] args) {        //创建线程池对象,使用Executors工厂类//public static ExecutorService newFixedThreadPool(int nThreads)ExecutorService pool = Executors.newFixedThreadPool(2) ;        //下来使用ExecutorService(跟踪多个异步任务)一些方法        //使用submit(Runnable target):提交多个任务        pool.submit(new MyRunnable()) ;        pool.submit(new MyRunnable()) ;        //结束线程池        pool.shutdown() ;    }}

多线程的第三种实现方式
实现Callable接口

package prac04;import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;public class Prac04 {public static void main(String[] args) throws InterruptedException, ExecutionException {    ExecutorService pool = Executors.newFixedThreadPool(2) ;   //相当于start()Future<Integer>f1=pool.submit(new MyCallable(100));Integer i1= f1.get();Future<Integer>f2=pool.submit(new MyCallable(10));Integer i2= f2.get();    System.out.println(i1);    System.out.println(i2);   pool.shutdown();}}package prac04;import java.util.concurrent.Callable;public class MyCallable implements Callable<Integer>{    private int number ;    public MyCallable(int number){        this.number = number ;    }    @Override    public Integer call() throws Exception {        int sum=0;        for(int x = 0 ; x < number ; x ++){        sum+=x;        }        return sum;    }}

定时器 Timer:

public void schedule(TimerTask task,Date time)安排在指定的时间执行指定的任务
public void schedule(TimerTask task, long delay)在多少毫秒后执行指定任务
public void schedule(TimerTask task, long delay, long period)
在多少毫秒后,执行任务,并且每个多少毫秒重复执行
public void cancel()终止此计时器，丢弃所有当前已安排的任务