Java线程

一,线程的实现：

1. 继承 Thread 类，重写runnable方法
2. 实现runnable接口，实现runnable方法
3. 通过Callable和FutureTask创建线程
4. 通过线程池创建线程

//-- 1.继承Thread类
public class ThreadExtendsThread extends Thread {

	@Override
	public void run() {
		for (int i = 0; i < 30; i++) {
			System.out.println("run :" + i);
		}
	}

	public static void main(String[] args) throws InterruptedException {
		System.out.println("main");
		Thread thread = new ThreadExtendsThread();
		thread.start();
		for (int i = 'a'; i <= 'z'; i++)
			System.out.println("main:" + (char) i);
	}

}
//-- 2.实现runnable接口
public class ThreadImplementsRunnable implements Runnable {

	@Override
	public void run() {
		for (int i = 0; i < 30; i++)
			System.out.println("run :" + i);
	}

	public static void main(String[] args) {
		Runnable runnable = new ThreadImplementsRunnable();
		Thread thread2 = new Thread(runnable);
		thread2.start();

		for (int i = 0; i < 30; i++)
			System.out.println("main:" + i);
	}

}

//-- 3.callable
public class ThreadImplementCallable implements Callable<String>{

	@Override
	public String call() throws Exception {
		System.out.println("callable....");
		Thread.sleep(1000);
		return "call";
	}
	
	public static void main(String[] args) throws Exception {
		ThreadImplementCallable callable = new ThreadImplementCallable();
		FutureTask<String> task = new FutureTask<String>(callable);
		new Thread(task).start();
		String str = task.get();
		System.out.println(str);
	}
}

//-- 4.线程池
public class Main {
	public static void main(String[] args) {
		ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 20, 200, TimeUnit.MILLISECONDS,
				new ArrayBlockingQueue<Runnable>(5));
		for (int i = 0; i < 20; i++) {
			Task task = new Task(i);
			executor.execute(task);
			System.out.println("线程池中线程的数目：" + executor.getPoolSize() + ", 队列中等待执行的任务数目：" + executor.getQueue().size()
					+ ", 已经执行完的任务数目：" + executor.getCompletedTaskCount());
		}
	}
}

class Task implements Runnable {
	private int taskNum;

	public Task(int num) {
		this.taskNum = num;
	}

	@Override
	public void run() {
		System.out.println("正在执行task " + taskNum);
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("task " + taskNum + "执行完毕");
	}
}

二,线程的状态：

https://www.cnblogs.com/hejing-swust/p/8038263.html

1. 新建 : 刚new出对象
2. 可运行 :
3. 运行
4. 阻塞
5. 死亡

三,线程的优先级:

public class ThreadPriority {

	public static void main(String[] args) {
		Thread ta = new Thread(new Runnable() {
			@Override
			public void run() {
				for (int i = 0; i < 20; i++) {
					System.out.println("ThreadA : " + i);
				}
			}
		});
		Thread tb = new Thread(new Runnable() {
			@Override
			public void run() {
				for (char i = 'a'; i < 'z'; i++) {
					System.out.println("ThreadB : " + i);
				}
			}
		});
		
		ta.setPriority(10);
		tb.setPriority(1);
		ta.start();
		tb.start();

	}
}

四,线程调度:

1. Thread.sleep():睡眠
2. wait();
3. notify();
4. notifyAll();

sleep() 和 wait()的区别：

• sleep休眠，只让出cpu的使用权，任然锁住对象
• wait（）让出锁，但是时间到了后会拿回锁
• sleep睡醒后不一定立即执行
• wait()使用notify或者notifyAlll或者指定睡眠时间来唤醒当前等待池中的线程。
• wiat()必须放在synchronized block中，否则会在program runtime时抛出”java.lang.IllegalMonitorStateException“异常。