public class MyThread extends Thread {

  @Override
  public void run() {
    while (true) {
      System.out.println(this.currentThread().getName());
    }
  }

  public static void main(String[] args) {
    MyThread thread = new MyThread();
    thread.start(); //线程启动的正确方式
  }
}

Thread-0
Thread-0
Thread-0
...

public class MyRunnable implements Runnable {

  @Override
  public void run() {
    System.out.println("123");
  }

  public static void main(String[] args) {
    MyRunnable myRunnable = new MyRunnable();
    Thread thread = new Thread(myRunnable, "t1");
    thread.start();
  }
}

public class MyThread extends Thread {
 private int count = 5;
 @Override
   public void run() {
  count--;
  System.out.println(this.currentThread().getName() + " count:" + count);
 }
 public static void main(String[] args) {
  MyThread myThread = new MyThread();
  Thread thread1 = new Thread(myThread, "thread1");
  Thread thread2 = new Thread(myThread, "thread2");
  Thread thread3 = new Thread(myThread, "thread3");
  Thread thread4 = new Thread(myThread, "thread4");
  Thread thread5 = new Thread(myThread, "thread5");
  thread1.start();
  thread2.start();
  thread3.start();
  thread4.start();
  thread5.start();
 }
}

thread3 count:2
thread4 count:1
thread1 count:2
thread2 count:3
thread5 count:0

public class MyThread extends Thread {

  private int count = 5;

  @Override
  public synchronized void run() {
    count--;
    System.out.println(this.currentThread().getName() + " count:" + count);
  }

  public static void main(String[] args) {
    MyThread myThread = new MyThread();
    Thread thread1 = new Thread(myThread, "thread1");
    Thread thread2 = new Thread(myThread, "thread2");
    Thread thread3 = new Thread(myThread, "thread3");
    Thread thread4 = new Thread(myThread, "thread4");
    Thread thread5 = new Thread(myThread, "thread5");
    thread1.start();
    thread2.start();
    thread3.start();
    thread4.start();
    thread5.start();
  }
}

thread1 count:4
thread2 count:3
thread3 count:2
thread5 count:1
thread4 count:0

public class MultiThread {

  private int num = 200;

  public synchronized void printNum(String threadName, String tag) {
    if (tag.equals("a")) {
      num = num - 100;
      System.out.println(threadName + " tag a,set num over!");
    } else {
      num = num - 200;
      System.out.println(threadName + " tag b,set num over!");
    }
    System.out.println(threadName + " tag " + tag + ", num = " + num);
  }

  public static void main(String[] args) throws InterruptedException {
    final MultiThread multiThread1 = new MultiThread();
    final MultiThread multiThread2 = new MultiThread();

    new Thread(new Runnable() {
      public void run() {
        multiThread1.printNum("thread1", "a");
      }
    }).start();

    Thread.sleep(5000);
    System.out.println("等待5秒，确保thread1已经执行完毕！");

    new Thread(new Runnable() {
      public void run() {
        multiThread2.printNum("thread2", "b");
      }
    }).start();
  }
}

thread1 tag a,set num over!
thread1 tag a, num = 100
等待5秒，确保thread1已经执行完毕！
thread2 tag b,set num over!
thread2 tag b, num = 0

public class MultiThread {

  private static int num = 200;

  public static synchronized void printNum(String threadName, String tag) {
    if (tag.equals("a")) {
      num = num - 100;
      System.out.println(threadName + " tag a,set num over!");
    } else {
      num = num - 200;
      System.out.println(threadName + " tag b,set num over!");
    }
    System.out.println(threadName + " tag " + tag + ", num = " + num);
  }

  public static void main(String[] args) throws InterruptedException {
    final MultiThread multiThread1 = new MultiThread();
    final MultiThread multiThread2 = new MultiThread();

    new Thread(new Runnable() {
      public void run() {
        multiThread1.printNum("thread1", "a");
      }
    }).start();

    Thread.sleep(5000);
    System.out.println("等待5秒，确保thread1已经执行完毕！");

    new Thread(new Runnable() {
      public void run() {
        multiThread2.printNum("thread2", "b");
      }
    }).start();
  }
}

thread1 tag a,set num over!
thread1 tag a, num = 100
等待5秒，确保thread1已经执行完毕！
thread2 tag b,set num over!
thread2 tag b, num = -100

public class MyObject {

  public void method() {
    System.out.println(Thread.currentThread().getName());
  }

  public static void main(String[] args) {
    final MyObject myObject = new MyObject();

    Thread t1 = new Thread(new Runnable() {
      public void run() {
        myObject.method();
      }
    }, "t1");

    Thread t2 = new Thread(new Runnable() {
      public void run() {
        myObject.method();
      }
    }, "t2");

    t1.start();
    t2.start();
  }
}