第五章我们可以直接调用run()方法来启动一个新线程吗|

不，你不能直接调用run方法来启动一个线程。您需要调用 start 方法来创建一个新线程。 如果你直接调用run方法，它不会创建一个新线程，它会和main在同一个栈中。 让我们在示例的帮助下理解：

package org.arpit.java2blog;
class CustomThread extends Thread {

public void run() {
  for (int i = 0; i < 5; i++) {
   try {
    Thread.sleep(300);
   } catch (InterruptedException e) {

    e.printStackTrace();
   }
   System.out.println("Thread is running :"+i);
  }

}

}

public class StartThreadAgainMain {

public static void main(String[] args) {
  CustomThread ct1 = new CustomThread();
  CustomThread ct2 = new CustomThread();
  ct1.run();
  ct2.run();

}

}

当您运行上面的程序时，您将得到以下输出：

Thread is running :0
Thread is running :1
Thread is running :2
Thread is running :3
Thread is running :4
Thread is running :0
Thread is running :1
Thread is running :2
Thread is running :3
Thread is running :4

正如您所看到的，当我们直接调用 run 方法时，它并没有创建新线程。

如果您在上面的示例中使用 start 而不是 run：

package org.arpit.java2blog;
class CustomThread extends Thread {

public void run() {
  for (int i = 0; i < 5; i++) {
   try {
    Thread.sleep(300);
   } catch (InterruptedException e) {

    e.printStackTrace();
   }
   System.out.println("Thread is running :"+i);
  }

}

}

public class StartThreadAgainMain {

public static void main(String[] args) {
  CustomThread ct1 = new CustomThread();
  CustomThread ct2 = new CustomThread();
  ct1.start();
  ct2.start();

}

}

当您运行上面的程序时，您将得到以下输出：

Thread is running :0
Thread is running :0
Thread is running :1
Thread is running :1
Thread is running :2
Thread is running :2
Thread is running :3
Thread is running :3
Thread is running :4
Thread is running :4

不能直接调用run方法创建线程，需要调用start方法创建新线程。