Callable接口中何时执行call方法

import  java.util.ArrayList;
import  java.util.concurrent.Callable;
import  java.util.concurrent.ExecutionException;
import  java.util.concurrent.ExecutorService;
import  java.util.concurrent.Executors;
import  java.util.concurrent.Future;
import  java.util.concurrent.TimeUnit;

class  TaskWithResult  implements  Callable{
    private  int  id;
    private  static  int  count = 10 ;
    private  final  int  time =count--;
    public  TaskWithResult( int  id){
        this .id = id;
    }

    @Override
    public  String call()  throws  Exception {
        TimeUnit.MILLISECONDS.sleep( 100 );
        return  "Result of TaskWithResult : " + id+ ", Time= " +time;
    }

}
public  class  CallableDemo {

    public  static  void  main(String[] args)  throws  InterruptedException, ExecutionException {
         ExecutorService exec = Executors.newCachedThreadPool();
         ArrayList> results = new  ArrayList>();
         for ( int  i= 0 ;i< 10 ;i++){
             results.add(exec.submit( new  TaskWithResult(i)));
         }

         for (Future fs : results){
             System.out.println(fs.get());
         }
    }

}

经测试表面，call（）方法的执行应是在exec.submit的时候调用的。也及时在线程被执行的时候执行call方法里面的东西。但这里有个问题如果启了多个线程，给call方法上打了断点，测试结果并不是每个线程执行的时候断点都会走call方法，应该是内部也有线程进行维护。我的理解就到这，希望懂的大神再帮忙解释下。