java加密 32字节256位的加密 16字节128位的加密

package com.util;


import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Md5DigestUtil {

	public static String md5Bit256(String plainText) {
		try {
			// 可以是 SHA-1" 或者 "MD5"
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(plainText.getBytes());
			byte b[] = md.digest();

			int i;

			StringBuffer buf = new StringBuffer("");
			for (int offset = 0; offset < b.length; offset++) {
				i = b[offset];
				if (i < 0)
					i += 256;
				if (i < 16)
					buf.append("0");
				buf.append(Integer.toHexString(i));
			}

			return buf.toString();// 32字节256位的加密

		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}

	public static String md5Bit128(String plainText) {
		try {
			// 可以是 SHA-1" 或者 "MD5"
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(plainText.getBytes());
			byte b[] = md.digest();

			int i;

			StringBuffer buf = new StringBuffer("");
			for (int offset = 0; offset < b.length; offset++) {
				i = b[offset];
				if (i < 0)
					i += 256;
				if (i < 16)
					buf.append("0");
				buf.append(Integer.toHexString(i));
			}

			return buf.toString().substring(8, 24); // 16字节128位的加密

		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}

	public static String md5Bit2562(String plainText) {
		try {
			// 可以是 SHA-1" 或者 "MD5"
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(plainText.getBytes());
			byte b[] = md.digest();

			int i;

			StringBuffer buf = new StringBuffer("");
			for (int offset = 0; offset < b.length; offset++) {
				i = b[offset];
				if (i < 0)
					i += 256;
				if (i < 16)
					buf.append("0");
				buf.append(Integer.toHexString(i));
			}

			return buf.toString();// 32字节256位的加密

		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}

	public static void main(String[] args) {
		System.out.println(Md5DigestUtil.md5Bit128("test"));
	}
}