java线程基础知识汇总

1.线程的状态

public enum State {
    /**
     * Thread state for a thread which has not yet started.
     */
    NEW,

    /**
     * Thread state for a runnable thread.  A thread in the runnable
     * state is executing in the Java virtual machine but it may
     * be waiting for other resources from the operating system
     * such as processor.
     */
    RUNNABLE,

    /**
     * Thread state for a thread blocked waiting for a monitor lock.
     * A thread in the blocked state is waiting for a monitor lock
     * to enter a synchronized block/method or
     * reenter a synchronized block/method after calling
     * {@link Object#wait() Object.wait}.
     */
    BLOCKED,

    /**
     * Thread state for a waiting thread.
     * A thread is in the waiting state due to calling one of the
     * following methods:
     * <ul>
     *   <li>{@link Object#wait() Object.wait} with no timeout</li>
     *   <li>{@link #join() Thread.join} with no timeout</li>
     *   <li>{@link LockSupport#park() LockSupport.park}</li>
     * </ul>
     *
     * <p>A thread in the waiting state is waiting for another thread to
     * perform a particular action.
     *
     * For example, a thread that has called {@code Object.wait()}
     * on an object is waiting for another thread to call
     * {@code Object.notify()} or {@code Object.notifyAll()} on
     * that object. A thread that has called {@code Thread.join()}
     * is waiting for a specified thread to terminate.
     */
    WAITING,

    /**
     * Thread state for a waiting thread with a specified waiting time.
     * A thread is in the timed waiting state due to calling one of
     * the following methods with a specified positive waiting time:
     * <ul>
     *   <li>{@link #sleep Thread.sleep}</li>
     *   <li>{@link Object#wait(long) Object.wait} with timeout</li>
     *   <li>{@link #join(long) Thread.join} with timeout</li>
     *   <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
     *   <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
     * </ul>
     */
    TIMED_WAITING,

    /**
     * Thread state for a terminated thread.
     * The thread has completed execution.
     */
    TERMINATED;
}

2.sleep与wait区别

sleep会让出cpu，但是不会让出锁；

wait会让出cpu及锁；

3.notify与notifyall区别

线程阻塞时会，会加入到锁池；

执行wait之后会加入到等待池；

notify执行之后，会在等待池之中随机挑选一个线程进入锁池，开始竞争锁；

notifyall执行之后，会将等待池中所有的线程放到锁池，参与竞争锁；

4.yield方法

会向线程调度器暗示自己让出cpu，但线程调度器并不一定同意；

5.终止线程方法；

原来采用stop方法，现在使用中断函数：

如果在锁池中，立马抛出中断异常；如果在runing之中，继续执行，需要程序自己判断处理异常；

6.线程转换图：