java多线程中捕获异常

/* 编写一个测试程序，用多线程计算1万以内素数之和与完全数之和的乘积。  
 */
 import java.lang.Thread;
 class PrimeAdd extends Thread{
     long a=0;//用来计算素数之和
     public boolean isPrime(int i){//判断是否是素数
         int count=0,  j;
          for( j=1;j<=i;j++){
             if(i%j==0)
                 count++;
         }
         if(count==2)
             return true;
         else 
             return false;
     }
     public void run(){
         //try{
             for(int i=1;i<10000;i++){
              if(isPrime(i))
                  a+=i;
          }
          System.out.println(a);
      //    }
          //catch(InterruptedException e){}
      }
          public long get(){
         return a;
     }
 }
 class CompleteAdd extends Thread{
     long b=0;//用来计算完全数之和
     public boolean isComplete(int i){
         int count=0,  j;
          for(j=1;jif(i%j==0)
             count+=j;    
         }
         if(count==i)
             return true;
         else
             return false;
     }
     public void run(){
         //try{
             for(int i=1;i<10000;i++){
                 if( isComplete(i))
                 b+=i;    
             }
                   System.out.println(b);
      //    }
      //    catch(InterruptedException e){}
     }
     public long get(){
         return b;
     }
 }
public class theProduct extends Thread {
    
    public static void main(String[] args) {
        PrimeAdd threadA=new PrimeAdd();
        CompleteAdd threadB =new CompleteAdd();
        threadA.start();
        threadA.join();
           threadB.start();
          threadB.join();
System.out.println(threadA.get()*threadB.get());
      }
}

这里给我报的错是

我知道要捕获异常，但是不知道在哪里加try.catch

join() 方法周围添加一个 try-catch 块

public static void main(String[] args) {
    PrimeAdd threadA = new PrimeAdd();
    CompleteAdd threadB = new CompleteAdd();
    threadA.start();
    try {
        threadA.join();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    threadB.start();
    try {
        threadB.join();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println(threadA.get() * threadB.get());
}