下面的代码实现了MD5值的生成：

public class MD5Test2 {	public static void main(String[] args) {		System.out.println(MD5Test2.MD5Operation("hello"));		System.out.println(MD5Test2.getMD5("hello"));	}        //通过java.math包的BigInteger类实现十六进制的转换	public final static String MD5Operation(String s){		try {			byte strTemp[] = s.getBytes();			MessageDigest md = MessageDigest.getInstance("MD5");			md.update(strTemp);			byte b[] = md.digest();						BigInteger bigInt = new BigInteger(1, b);			return bigInt.toString(16);					} catch (NoSuchAlgorithmException e) {			return null;		}	}        //利用java底层代码实现十六进制的转换	public final static String getMD5(String s) {		char hexDigits[] = {                ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘,                ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘};		try {			byte strTemp[] = s.getBytes();			MessageDigest md = MessageDigest.getInstance("MD5");			md.update(strTemp);			byte b[] = md.digest();						int len = b.length;			char str[] = new char[len*2];			int k=0;			for(int i=0; i<len; i++){				str[k++] = hexDigits[b[i] >>> 4 & 0xf];				str[k++] = hexDigits[b[i] & 0xf];			}			return new String(str);					} catch (NoSuchAlgorithmException e) {			return null;		}	}}