Largest prime factor program takes aaaages - Java

Question

So this is problem 3 from project Euler. For those who don\'t know, I have to find out the largest prime factor of 600851475143. I have the below code:

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Answer 1

public class LargestPrimeFactor {

public static boolean isPrime(long num){
    int count = 0;
    for(long i = 1; i<=num/2 ; i++){
        if(num % i==0){
            count++;
        }
    }
    if(count==1){
        return true;
    }
    return false;
}

public static String largestPrimeFactor(long num){
    String factor = "none";
    for(long i = 2; i<= num/2 ; i++){
        if(num % i==0 && isPrime(i)){
           factor = Long.toString(i); 
        }
    }
    return factor;     
}
public static void main(String[] args) {
    System.out.println(largestPrimeFactor(13195));
}

}