Java实现MD5加密

public class MD5Test {
	/**
	 * 对明文字符串进行MD5加密
	 * @param source 传入的明文字符串
	 * @return 加密结果
	 */
	public static String md5(String source) {
		// 1.判断source是否有效
		if(source == null || source.length() == 0 ) {
			//2.如果不是有效的字符串抛出异常
			throw new RuntimeException("不是有效字符串");
		}
		
		
		try {
			//3.获取MessageDigest对象
			String algorithm = "md5";
		
			MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
			
			//4.获取明文字符串对应的字节数组
			byte[] input = source.getBytes();
			//5.执行加密
			byte[] output = messageDigest.digest(input);
			//6.创建BigInteger对象
			int signum = 1;
			BigInteger bigInteger = new BigInteger(signum,output);
			//7.按照16进制将bigInteger的值转换为字符串
			int radix = 16;
			String encoded = bigInteger.toString(radix).toUpperCase();
			
			return encoded;
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		
		return null;
	}
	
	
	public static void main(String[] args) {
		String sourceString = "123456";
		System.out.println(MD5Test.md5(sourceString));
	}
}