SOExample, Java - rextester

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//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;
import java.security.MessageDigest;

class Rextester
{  
    public static void main(String args[]) throws Exception
    {
        byte[] result = hash("johntest".getBytes(), "john".getBytes(), 2);        
        System.out.println(bytesToHex(result));
    }
    
    protected static byte[] hash(byte[] bytes, byte[] salt, int hashIterations) throws Exception {
        MessageDigest digest = MessageDigest.getInstance("MD5");
        if (salt != null) {
            digest.reset();
            digest.update(salt);
        }
        byte[] hashed = digest.digest(bytes);
        int iterations = hashIterations - 1; //already hashed once above
        //iterate remaining number:
        for (int i = 0; i < iterations; i++) {
            digest.reset();
            hashed = digest.digest(hashed);
        }
        return hashed;
    }

private static String bytesToHex(byte[] hashInBytes) {

StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hashInBytes.length; i++) {
            sb.append(Integer.toString((hashInBytes[i] & 0xff) + 0x100, 16).substring(1));
        }
        return sb.toString();

}
}

[ + ] Show input
Compilation time: 0.63 sec, absolute running time: 0.16 sec, cpu time: 0.14 sec, memory peak: 20 Mb, absolute service time: 0,8 sec