public class Object {    //注册本地函数，方可以从库中的本机代码调用JNI函数    private static native void registerNatives();    static {        registerNatives();    }
    /**     * Constructs a new object.     */     //HotSpotIntrinsicCandidate注解，说明本方法，jvm额外维护了一个利用了CPU指令的高效实现    @HotSpotIntrinsicCandidate    public Object() {}
    //返回对象的运行时类型    /**     * Number c = 0;     * Class<? extends  Number> clazz = c.getClass();     * System.out.println(clazz);     * 打印如下：     * class java.lang.Integer     * 关于泛型及泛型擦除概念，见后续泛型章节     */    @HotSpotIntrinsicCandidate    public final native Class<?> getClass();
     /**     * 返回对象的hash码，hashCode方法支持hash表（比如java.util.HashMap）的特性，     * 不同的对象返回唯一的has码，可以提高hash表数据结构的性能。     * hashCode有时候以对象内存地址的机制生成，有时候不是     * java.lang.System.identityHashCode 工具方法 返回默认hashCode()方法的值，null引用返回的hash码为0     */     @HotSpotIntrinsicCandidate    public native int hashCode();
    /**    * 标示其他对象与当前对象是否相等    * 自反性: 自己（非null）与自己比较永远相当    * 对称性: x vs y or y vs x 等价    * 可传递: x.equals(y) == true and y.equals(z), then x.equals(z)    * 一致性: 一旦x.equals(y) == true, then anytime x.equals(y) == true    * any not null value not equals null    * 如果覆盖equals方法，一定要覆盖hashCode方法    */    public boolean equals(Object obj) {        return (this == obj);    }
    /**     * clone返回会返回一个相同类型的新对象拷贝，如果要实现克隆，那么当前类及其父类需要实现cloneable接口。     * 对于复杂类型，默认的clone方式仅实现”浅克隆”，如果要实现”深克隆”，需要覆盖clone方法。     * 注：在软件编程中，推荐使用工具类的方式做copy，而不是覆盖clone的方式          */    @HotSpotIntrinsicCandidate    protected native Object clone() throws CloneNotSupportedException;
    /**    * 默认返回 getClass().getName() + '@' + Integer.toHexString(hashCode())    * 具体类可以覆盖Object的toString()方法    */    public String toString() {        return getClass().getName() + "@" + Integer.toHexString(hashCode());    }
    /**     * 持有该对象锁的线程通过调用notify唤醒等待此对象监视器的某一个线程，选择是随机的（具体由不同虚拟机实现）。一次只能有一个线程持有对象锁。     * 获取对象锁定三种方式如下：
     * 1，通过执行该对象的同步实例方法     * 2，通过执行该对象的同步代码块     * 3，通过执行类的同步静态方法     * 见 /openjdk/hotspot/src/share/vm/prims/jvm.cpp line: 526~530     * 见 /openjdk/hotspot/src/share/vm/runtime/synchronizer.cpp line: 407~411     * @throws  IllegalMonitorStateException  if the current thread is not     *               the owner of this object's monitor.     * @see        java.lang.Object#notifyAll()     * @see        java.lang.Object#wait()     */    @HotSpotIntrinsicCandidate    public final native void notify();
    /**     * 持有该对象锁的线程通过调用notify唤醒等待此对象监视器的所有线程。当当前线程释放对象监视器后，其他唤醒的线程会竞争对象监视器。     *     * @throws  IllegalMonitorStateException  if the current thread is not     *               the owner of this object's monitor.     * @see        java.lang.Object#notify()     * @see        java.lang.Object#wait()     */    @HotSpotIntrinsicCandidate    public final native void notifyAll();
    /**     * 调用此方法会导致当前对象进入等待状态，知道被其他线程唤醒（notify）或中断（InterruptedException）。相当于wait(0L)     *     * @throws IllegalMonitorStateException if the current thread is not     *         the owner of the object's monitor     * @throws InterruptedException if any thread interrupted the current thread before or     *         while the current thread was waiting. The <em>interrupted status</em> of the     *         current thread is cleared when this exception is thrown.     * @see    #notify()     * @see    #notifyAll()     * @see    #wait(long)     * @see    #wait(long, int)     */    public final void wait() throws InterruptedException {        wait(0L);    }
    /**     *      * @param  timeoutMillis the maximum time to wait, in milliseconds     * @throws IllegalArgumentException if {@code timeoutMillis} is negative     * @throws IllegalMonitorStateException if the current thread is not     *         the owner of the object's monitor     * @throws InterruptedException if any thread interrupted the current thread before or     *         while the current thread was waiting. The <em>interrupted status</em> of the     *         current thread is cleared when this exception is thrown.     * @see    #notify()     * @see    #notifyAll()     * @see    #wait()     * @see    #wait(long, int)     */    public final native void wait(long timeoutMillis) throws InterruptedException;
    /**     *  在并发编程章节重点讲解     * @param  timeoutMillis the maximum time to wait, in milliseconds     * @param  nanos   additional time, in nanoseconds, in the range range 0-999999 inclusive     * @throws IllegalArgumentException if {@code timeoutMillis} is negative,     *         or if the value of {@code nanos} is out of range     * @throws IllegalMonitorStateException if the current thread is not     *         the owner of the object's monitor     * @throws InterruptedException if any thread interrupted the current thread before or     *         while the current thread was waiting. The <em>interrupted status</em> of the     *         current thread is cleared when this exception is thrown.     * @see    #notify()     * @see    #notifyAll()     * @see    #wait()     * @see    #wait(long)     */    public final void wait(long timeoutMillis, int nanos) throws InterruptedException {        if (timeoutMillis < 0) {            throw new IllegalArgumentException("timeoutMillis value is negative");        }
        if (nanos < 0 || nanos > 999999) {            throw new IllegalArgumentException(                                "nanosecond timeout value out of range");        }
        if (nanos > 0) {            timeoutMillis++;        }
        wait(timeoutMillis);    }
    /**     * 通知垃圾回收器当前对应已经没有引用了，具体回收还要看jvm内部实现。     * jdk9 标记为已过时，在jvm原理章节重点讲解     *     * @throws Throwable the {@code Exception} raised by this method     * @see java.lang.ref.WeakReference     * @see java.lang.ref.PhantomReference     * @jls 12.6 Finalization of Class Instances     */    @Deprecated(since="9")    protected void finalize() throws Throwable { }}

5. 将本地方法编写的文件生成动态链接库    ```shell    gcc -dynamiclib -I /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home/include TestJNIImpl.c -o libhello.jnilib