Java native关键字

今天研究object源码的时候，碰到了native关键字。 简单的说就是本地方法，当在方法中调用一些不是由java语言写的代码或者在方法中用java语言,直接操纵计算机硬件时要声明为native方法。

以下是object源码，

    private static native void registerNatives();
    static {
        registerNatives();
    }
    public final native Class<?> getClass();
    public native int hashCode();

    public boolean equals(Object obj) {
    return (this == obj);
    }
    protected native Object clone() throws CloneNotSupportedException;
    public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }   //初学Java时，对对象tostring时候，一直疑惑@后面跟一串数字是什么，原来是hashcode

    public final native void notify();
    public final native void notifyAll();
    public final native void wait(long timeout) throws InterruptedException;

    public final void wait(long timeout, int nanos) throws InterruptedException {
        if (timeout < 0) {
            throw new IllegalArgumentException("timeout value is negative");
        }

        if (nanos < 0 || nanos > 999999) {
            throw new IllegalArgumentException(
                "nanosecond timeout value out of range");
        }

    if (nanos >= 500000 || (nanos != 0 && timeout == 0)) {
        timeout++;
    }

    wait(timeout);
    }

    public final void wait() throws InterruptedException {
    wait(0);
    }

    protected void finalize() throws Throwable { }