多线程：创建Thread为什么要调用start启动，而不能直接调用run方法

package com.example.wangchuncheng.myservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

public class MyService extends Service {

private boolean running = false;
private String data  = "这是默认信息";

public MyService() {
}

@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
throw new UnsupportedOperationException("Not yet implemented");
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
data = intent.getStringExtra("data");
return super.onStartCommand(intent, flags, startId);
}

@Override
public void onCreate() {
super.onCreate();
running = true;

new Thread(){
@Override
public void run() {
super.run();
while(running){
System.out.println(data);
try {
sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
//这里使用run的话，开始服务后会卡死，导致程序无响应
}

@Override
public void onDestroy() {
super.onDestroy();
running = false;
}
}