多线程 - yield()能立马让线程让出CPU时间片么？

答案：不能

线程之间的关系，是“协同式”的，不是“抢占式”的。

yield不会强制让渡CPU， interrupt也不会强制停止线程。

根据源码注释：

• 调用yield，只是想处理器processor暗示：“当前线程愿意让渡yield时间片”。但是处理器可以自由的忽略这个暗示。
• 这就说明了：线程之间的关系，是“协同式”的，不是“抢占式”的
• yield方法对于debugging或者testing的帮助很大，可以帮助减少由于竞争条件造成的bug

/**
     * A hint to the scheduler that the current thread is willing to yield
     * its current use of a processor. The scheduler is free to ignore this
     * hint.
     *
     * <p> Yield is a heuristic attempt to improve relative progression
     * between threads that would otherwise over-utilise a CPU. Its use
     * should be combined with detailed profiling and benchmarking to
     * ensure that it actually has the desired effect.
     *
     * <p> It is rarely appropriate to use this method. It may be useful
     * for debugging or testing purposes, where it may help to reproduce
     * bugs due to race conditions. It may also be useful when designing
     * concurrency control constructs such as the ones in the
     * {@link java.util.concurrent.locks} package.
     */
    public static native void yield();