MD5 collision test

HashCodeUtil.java

import java.security.MessageDigest;
import java.util.HashMap;
 
public class HashCodeUtil {
    private static HashMap<String,String> collisionMap ;
    public static String getHashcode(String input) {
        MessageDigest hasher = null;
        try {
            hasher = MessageDigest.getInstance("MD5");
            //hasher = MessageDigest.getInstance("SHA-256");
        } catch (Exception e) {
            System.out.println("Could not get MD5 Hasher for calculating hashcodes:" + e.getMessage());
            return null;
        }
        hasher.update(input.getBytes());
        byte[] buffer = hasher.digest();
        int[] intVal = new int[4];
        for (int i=0, j = 0; j < 16; i++, j += 4) {
            intVal[i] = ((int) (buffer[j] & 0xff)) +
                    (((int) (buffer[j + 1] & 0xff)) << 8) +
                    (((int) (buffer[j + 2] & 0xff)) << 16) +
                    (((int) (buffer[j + 3] & 0xff)) << 24);
        }
        int hashInt = intVal[0] ^ intVal[1] ^ intVal[2] ^ intVal[3];
        if (hashInt == 0) {
            hashInt = 0xFFFFFFFF;
        }
        return"0x" + Integer.toHexString(hashInt);
    }
 
    public  static void  main(String[] args) {
 
        int sum = 0;
        for (int j = 0; j < 100; j++) {
            HashMap<String,String>  collisionMap = new HashMap<String, String>(70000);
            for (int i = 0; i < 100000000; i++) {
                String input = "Hello"+i+","+j;
                String hash = getHashcode(input);
                if(collisionMap.get(hash) == null) {
                    collisionMap.put(hash,input);
                } else {
                    System.out.println(input + "," +collisionMap.get(hash) + "," + i );
                    sum += i;
                    break;
                }
            }
        }
        System.out.println(sum / 100. + " iterations on average");
    }
}