获取文件的Hash值代码实现

package com.hfq.house.manager.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util {

	protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e',
			'f' };
	protected static MessageDigest messagedigest = null;

	/**
	 * MessageDigest初始化
	 * 
	 * @author 高焕杰
	 */
	static {
		try {
//			messagedigest = MessageDigest.getInstance("MD5");
			messagedigest = MessageDigest.getInstance("SHA-1");
		} catch (NoSuchAlgorithmException e) {
			System.err.println("MD5FileUtil messagedigest初始化失败");
			e.printStackTrace();
		}
	}

	/**
	 * 对文件进行MD5加密
	 * 
	 * @author 高焕杰
	 */
	public static String getFileMD5String(File file) throws IOException {
		FileInputStream in = new FileInputStream(file);
		FileChannel ch = in.getChannel();
		MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
		messagedigest.update(byteBuffer);
		return bufferToHex(messagedigest.digest());
	}

	/**
	 * 对字符串进行MD5加密
	 * 
	 * @author 高焕杰
	 */
	public static String getMD5String(String s) {
		return getMD5String(s.getBytes());
	}

	/**
	 * 对byte类型的数组进行MD5加密
	 * 
	 * @author 高焕杰
	 */
	public static String getMD5String(byte[] bytes) {
		messagedigest.update(bytes);
		return bufferToHex(messagedigest.digest());
	}

	private static String bufferToHex(byte bytes[]) {
		return bufferToHex(bytes, 0, bytes.length);
	}

	private static String bufferToHex(byte bytes[], int m, int n) {
		StringBuffer stringbuffer = new StringBuffer(2 * n);
		int k = m + n;
		for (int l = m; l < k; l++) {
			char c0 = hexDigits[(bytes[l] & 0xf0) >> 4];
			char c1 = hexDigits[bytes[l] & 0xf];
			stringbuffer.append(c0);
			stringbuffer.append(c1);
		}
		return stringbuffer.toString();
	}

	public static void main(String[] args) throws IOException {
		String filePath = "/Users/jjs/Desktop/13.jpg";
		long fileBegin = System.currentTimeMillis();
		System.out.println("文件加密结果为：" + getFileMD5String(new File(filePath)));
		long fileEnd = System.currentTimeMillis();
		System.out.println("文件加密耗时:" + ((fileEnd - fileBegin)) + "ms");
		
	}
}