获取文件或者某个字符串的MD5 hash值

MD5Utils.java

package com.gkeeps.tools;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Utils {
	static MessageDigest MD5 = null;

	static {
		try {
			MD5 = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException ne) {
			ne.printStackTrace();
		}
	}

	/**
	 * 对一个文件获取md5值
	 * 
	 * @return md5串
	 */
	public static String getMD5(File file) {
		FileInputStream fileInputStream = null;
		try {
			fileInputStream = new FileInputStream(file);
			byte[] buffer = new byte[8192];
			int length;
			while ((length = fileInputStream.read(buffer)) != -1) {
				MD5.update(buffer, 0, length);
			}

			return new String(encodeHex(MD5.digest(), true));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
			return null;
		} catch (IOException e) {
			e.printStackTrace();
			return null;
		} finally {
			try {
				if (fileInputStream != null)
					fileInputStream.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 求一个字符串的md5值
	 * 
	 * @param srcString
	 *            字符串
	 * @return md5 value
	 */
	public static String getMD5(String srcString) {
		return encodeHexString(MD5.digest(srcString.getBytes(Charset.forName("utf-8"))));
	}

	private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
			'e', 'f' };
	private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
			'E', 'F' };

	private static String encodeHexString(final byte[] data) {
		return new String(encodeHex(data, true));
	}

	private static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
		return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
	}

	private static char[] encodeHex(final byte[] data, final char[] toDigits) {
		final int l = data.length;
		final char[] out = new char[l << 1];
		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
			out[j++] = toDigits[0x0F & data[i]];
		}
		return out;
	}

	public static void main(String[] args) {
		java.util.Date d = new java.util.Date();
		long t1 = d.getTime();
		String md5 = getMD5(
				new File("F:\\Downloads\\xxxxx_x86_and_x64_dvd.iso")); //1.7G
		d = new java.util.Date();
		long t2 = d.getTime();
		System.out.println(String.format("times: %s ms, md5 = %s", t2 - t1, md5));
	}
}