Java MD5 Super Collider is Super Slow

md5.java

import java.security.*;
import java.math.BigInteger;


public class md5 {

    private static MessageDigest md;
    private static final String charList = "0123456789abcdef";
    private static SecureRandom rand = new SecureRandom();
    private static final int numLoops = (int)1e6;
    private static final int numSigDigs = 4;

    public static void main(String[] args) throws Exception {
        md = MessageDigest.getInstance("MD5");
        String s = "";
        String hashed = "";
        int similarity = 0;

        for (int i=0; i < numLoops; i++) {
            s = randomHash();
            hashed = getMD5(s);

            similarity = compareStrings(s, hashed);
            if (similarity >= numSigDigs) {
                System.out.println(s + ":" + hashed);
            }
        }
    }

    private static String getMD5(String s) throws Exception {
        byte[] bytesOfMessage = s.getBytes("UTF-8");
        return String.format("%032x", new BigInteger(1, md.digest(bytesOfMessage)));
    }
    
    private static String randomHash(){
        StringBuilder sb = new StringBuilder(32);
        for(int i=0; i < 32; i++) {
            sb.append(charList.charAt(rand.nextInt(16)));
        }
        return sb.toString();
    }
    
    private static int compareStrings(String s1, String s2) {
        int i = 0;
        boolean found = true;
        while (found) {
            if (s1.charAt(i) == s2.charAt(i)) {
                i += 1;
            } else {
                found = false;
            }
        }
        return i;
    }
}