java 计算50以内所有素数的和？

boolean is ;
int sum = 0;
for(int j = 1;j <= 50; j++){
is = true;
for(int i = 2; i <= java.lang.Math.sqrt(j)+1; i++){
if((j%i) == 0) {
is = false;
break;
}
}
if(is){
sum+=j;
}
}
System.out.println(sum);

int a; int b=0;
for (int i = 1; i <=50; i++) {
for (a = 2; a <= (int)i/2; a++) {
if (i % a == 0) {
break;
}

}
if (a > (int)i/2 ) {
b+=i;
}
}
System.out.println(b);