Version: Next

Native关键字

新建一个线程，进入start()方法的源码

public class Demo01 {
    public static void main(String[] args) {
        new Thread(()->{
            
        },"my thread name").start();
    }
}

public synchronized void start() {
  /**
         * This method is not invoked for the main method thread or "system"
         * group threads created/set up by the VM. Any new functionality added
         * to this method in the future may have to also be added to the VM.
         *
         * A zero status value corresponds to state "NEW".
         */
  if (threadStatus != 0)
    throw new IllegalThreadStateException();

  /* Notify the group that this thread is about to be started
         * so that it can be added to the group's list of threads
         * and the group's unstarted count can be decremented. */
  group.add(this);

  boolean started = false;
  try {
    start0();
    started = true;
  } finally {
    try {
      if (!started) {
        group.threadStartFailed(this);
      }
    } catch (Throwable ignore) {
      /* do nothing. If start0 threw a Throwable then
                  it will be passed up the call stack */
    }
  }
}

private native void start0(); // 一个用native修饰的方法，像个接口方法一样，很诡异

注意

凡是带了native关键字的，表示Java的作用范围无法到达，去调用底层C语言的库

JNI Java Native Interface Java本地方法接口

凡是带了native关键字的方法，都会进入本地方法栈

Native Method Stack 本地方法栈

本地接口的作用是融合不同的编程语言为Java所用，它的初衷是融合C/C++程序，Java在诞生的时候还是C/C++横行的时代，想要立足，必须有调用C/C++程序的能力，于是就在内存中专门开辟了一块区域处理标记为native的代码。

他的具体做法是，在Native Method Stack中登记native方法，在执行引擎Execution Engine执行的时候加载Native Libraries

目前该方法使用的越来越少了，除非是与硬件有关的应用，比如通过Java程序驱动打印机或者Java系统管理生产设备，在企业级应用中已经比较少见

Native关键字#

注意

Native关键字