java编写两个线程，一个计算2到1000之间的素数，另一个计算1000到2000之间的素数。

class Thread1 implements Runnable {

@Override
public void run() {
// TODO Auto-generated method stub
int j;
for (int i = 2; i <= 1000; i++) {
j = 2;
for (; j <= Math.sqrt(i); j++) {
if (i % j == 0) {
break;
}
}
if (j > Math.sqrt(i))
System.err.println(i);
}
}

}

class Thread2 implements Runnable {

@Override
public void run() {
// TODO Auto-generated method stub
int j;
for (int i = 1001; i <= 2000; i++) {
j = 2;
for (; j <= Math.sqrt(i); j++) {
if (i % j == 0) {
break;
}
}
if (j > Math.sqrt(i))
System.err.println(i);
}
}

}

public class TwoThreadForPrime {
public static void main(String[] args) {
Thread t1 = new Thread(new Thread1());
Thread t2 = new Thread(new Thread