1.概念杂记
* runnable不叫线程，叫任务
* 继承和接口，一般优先选择接口
* 线程睡眠时会释放cpu
* 后台线程（守护线程）会因前台线程的结束而结束
* 线程优先级1-10，默认5
* 多线程同步机制必须使用同一把锁（即同一个对象）
* 同步方法使用的锁就是调用的对象this
* 多线程用StringBuffer,单线程用StringBuilder
* synchronized既能同步代码块，也能同步方法
* yield()是让出cpu，但是还可以再抢
* static synchronized的锁为类名.class（字节码文件）
* 单例模式安全性和效率解决方法：多重判断
* wait()等待，notify()唤醒
* wait()会释放锁，sleep不会释放锁
* wait()必须放在同步中
* 因为同步锁可以为任意锁或对象，所以wait方法在Object类下
* 同步嵌套同步，发生死锁的概率很大
* 哪个线程执行wait()，哪个线程就等待
2.线程两种启动方法
* 继承Thread类
class MyThread extends Thread{ @Override public void run() { XXX; } } public class ThreadDemo1 { public static void main(String[] args) { MyThread t1 = new MyThread(); t1.start(); } }
* 实现Runnable接口
public class MyRunnable implements Runnable { @Override public void run() { XXX； } } public class ThreadDemo2 { public static void main(String[] args) { MyRunnable runnable = new MyRunnable(); Thread t1 = new Thread(runnable); t1.start(); } }
3.多线程
* 继承Thread类
MyThread t1 = new MyThread(); MyThread t2 = new MyThread(); t1.start(); t2.start();
* 实现Runnable接口
MyRunnable runnable = new MyRunnable(); Thread t1 = new Thread(runnable); Thread t2 = new Thread(runnable); t1.start(); t2.start();
4.线程安全较高效率的单例模式
public class SingleInstance { private static SingleInstance single; private SingleInstance(){}//构造方法私有化为了不让别人new public static SingleInstance getInstance(){ if(single == null){ synchronized (SingleInstance.class) { if(single == null){ single = new SingleInstance(); } } } return single; } }
5.wait方法和sleep方法的区别
* 1:wait方法会释放锁，sleep方法不会释放锁。
* 2:wait必须放在同步中，sleep不一定放在同步中.
* 3:wait一般的情况是让对方唤醒。sleep通常会自己醒过来。
* 4:wait需要用锁去调用。sleep是用Thread类或者Thread对象来调用。
6.Condition
public static Lock lock = new ReentrantLock(); //创建一个Condition public static Condition p_con = lock.newCondition(); public static Condition c_con = lock.newCondition();
例子：
class BoundedBuffer { final Lock lock = new ReentrantLock(); final Condition notFull = lock.newCondition(); final Condition notEmpty = lock.newCondition(); final Object[] items = new Object[100]; int putptr, takeptr, count; public void put(Object x) throws InterruptedException { lock.lock(); try { while (count == items.length) notFull.await(); items[putptr] = x; if (++putptr == items.length) putptr = 0; ++count; notEmpty.signal(); } finally { lock.unlock(); } } public Object take() throws InterruptedException { lock.lock(); try { while (count == 0) notEmpty.await(); Object x = items[takeptr]; if (++takeptr == items.length) takeptr = 0; --count; notFull.signal(); return x; } finally { lock.unlock(); } } }
7.Executors-线程池
ExecutorService service = Executors.newFixedThreadPool(2); for(int i = 0;i<100;i++){ service.execute(new Runnable(){ @Override public void run() { for(int i = 0;i<100;i++){ System.out.println(Thread.currentThread().getName()+":"+i); } } }); }
8.线程的生命周期
原文：http://www.cnblogs.com/anni-qianqian/p/5223791.html