start方法和run方法启动线程
public class StartAndRunMethod {
public static void main(String[] args) {
Runnable runnable = () -> {
System.out.println(Thread.currentThread().getName());
};
runnable.run();
new Thread(runnable).start();
}
}
start()方法源码：
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 */
}
}
}
- 将该线程加入线程组
- 启动新线程
- 处于就绪状态，等待CPU分配资源
- 获取到CPU分配的资源后，系统会调用thread的run()方法执行线程
多个线程，调用start()方法的顺序，并不是真正执行线程的顺序。
run()方法
源码：
@Override
public void run() {
if (target != null) {
target.run();
}
}
启动线程要调用start()方法，间接的去调用run()方法
