java异常与线程

一、异常

　　finally存在的意义，不管try有没有出现异常，或者catch有没有捕获异常，finally都会执行

二、线程

　　创建多线程程序的第一种方法（继承Thread类，重写run方法）

public class A02thread extends Thread {
    public static void main(String[] args) {
        A02thread a02thread = new A02thread("子线程");//构造方法设置线程名称
        a02thread.start();

        Thread.currentThread().setName("主线程");//设置线程名称
        for (int i = 0; i < 10; i++) {
            try {
                Thread.sleep(1000);//线程睡眠
            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + ":" + i);//获取线程名称
        }
    }

    public A02thread() {
    }

    public A02thread(String name) {
        super(name);
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            try {
                Thread.sleep(1000);//线程睡眠
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(getName() + ":" + i);//获取线程名称
        }
    }
}

 　　创建多线程程序的第二种方法（实现Runable接口）

public class A02thread implements Runnable {
    public static void main(String[] args) {
        Runnable a02thread = new A02thread();
        Thread thread = new Thread(a02thread);
        thread.start();

        for (int i = 0; i < 10; i++) {
            System.out.println("主线程:" + i);
        }
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("子线程:" + i);
        }
    }
}

 　　备注：推荐接口方式，继承只能有一个，实现可以有多个。

　　匿名内部类方式

public class A02thread {
    public static void main(String[] args) {
        new Thread() {
            @Override
            public void run() {
                for (int i = 0; i < 10; i++) {
                    System.out.println(Thread.currentThread().getName() + ":" + i);
                }
            }
        }.start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 10; i++) {
                    System.out.println(Thread.currentThread().getName() + ":" + i);
                }
            }
        }).start();
    }
}

三、线程安全

　　同步代码块

public class A02thread implements Runnable {
    public static void main(String[] args) {
        A02thread a02thread = new A02thread();

        new Thread(a02thread).start();
        new Thread(a02thread).start();
        new Thread(a02thread).start();
    }

    private int resource = 10;

    private Object obj = new Object();//锁对象

    @Override
    public void run() {
        while (true) {
            synchronized (obj) {
                if (resource > 0) {
                    try {
                        Thread.sleep(50);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + ":" + resource);
                    resource--;
                }
            }
        }
    }
}

 　　同步方法

public class A02thread implements Runnable {
    public static void main(String[] args) {
        A02thread a02thread = new A02thread();

        new Thread(a02thread).start();
        new Thread(a02thread).start();
        new Thread(a02thread).start();
    }

    private int resource = 10;

    @Override
    public void run() {
        while (true) {
            threadrunmethod();
        }
    }

    public synchronized void threadrunmethod() {//锁对象为this,相当于synchronized (this){}
        if (resource > 0) {
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + ":" + resource);
            resource--;
        }
    }
}

 　　静态同步方法

public class A02thread implements Runnable {
    public static void main(String[] args) {
        A02thread a02thread = new A02thread();

        new Thread(a02thread).start();
        new Thread(a02thread).start();
        new Thread(a02thread).start();
    }

    private static int resource = 10;

    @Override
    public void run() {
        while (true) {
            threadrunmethod();
        }
    }

    public static synchronized void threadrunmethod() {//锁对象为当前类的class,相当于synchronized (A02thread.class){}
        if (resource > 0) {
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + ":" + resource);
            resource--;
        }
    }
}

四、线程状态（生产者与消费者例子）

public class practice {
    public static void main(String[] args) {
        Object obj = new Object();

        //生产者
        new Thread() {
            @Override
            public void run() {
                synchronized (obj) {
                    try {
                        obj.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("生产者开始造包子");
                    for (int i = 0; i < 3; i++) {
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println((i + 1) + "秒");
                    }
                    System.out.println("生产者造好包子");
                    obj.notify();
                }
            }
        }.start();

        //消费者
        new Thread() {
            @Override
            public void run() {
                synchronized (obj) {
                    System.out.println("消费者想要吃包子,等待生产者生产包子");
                    obj.notify();
                    try {
                        obj.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("消费者开始吃包子");
                }
            }
        }.start();
    }
}

五、线程池

public class Practice implements Runnable {
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newFixedThreadPool(2);
        threadPool.submit(new Practice());
        threadPool.submit(new Practice());
        threadPool.submit(new Practice());

        threadPool.shutdown();//不建议使用
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "执行线程任务");
    }
}