MD5 Hashing in Java,Written by dimport

A wrapper for Java's MD5 class that makes life a little easier.

This class lets you produce an MD5 hashcode for some binary data. It is useful for storing passwords in databases or file systems, or for checking the validity of downloaded files. It also provides an example of the singleton design pattern.

import java.security.*;

public class MD5
{

private MessageDigest md = null;
static private MD5 md5 = null;
private static final char[] hexChars ={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

/**
* Constructor is private so you must use the getInstance method
*/
private MD5() throws NoSuchAlgorithmException
{
md = MessageDigest.getInstance("MD5");
}

/**
* This returns the singleton instance
*/
public static MD5 getInstance()throws NoSuchAlgorithmException
{

if (md5 == null)
{
md5 = new MD5();

}

return (md5);
}

public String hashData(byte[] dataToHash)

{

return hexStringFromBytes((calculateHash(dataToHash)));
}

private byte[] calculateHash(byte[] dataToHash)

{
md.update(dataToHash, 0, dataToHash.length);

return (md.digest());
}

public String hexStringFromBytes(byte[] b)

{

String hex = "";

int msb;

int lsb = 0;
int i;

// MSB maps to idx 0

for (i = 0; i < b.length; i++)

{

msb = ((int)b[i] & 0x000000FF) / 16;

lsb = ((int)b[i] & 0x000000FF) % 16;
hex = hex + hexChars[msb] + hexChars[lsb];
}
return(hex);
}

public static void main(String[] args)
{
try
{

MD5 md = MD5.getInstance();
System.out.println(md.hashData("hello".getBytes()));
}
catch(NoSuchAlgorithmException e)
{
e.printStackTrace(System.out);
}
}
}