public static boolean isMD5( String str ) 
	throws NullPointerException {


	// MD5 hashes are 32 hex-characters long (representing 16 bytes)
	if( str.length() != 32 )
	    return false;


	// Each char must be a hex-character
	try {

	    for( int i = 0; i < str.length(); i++ ) {

		int tmp = hex2int( str.charAt(i) );

	    }
	    return true;

	} catch( NumberFormatException e ) {

	    return false;

	}
    }