java计算文件的MD5值

package phreadpool;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.Map;

public class FileMDFive {

	public static void main(String[] args) {

		System.out.println(FileMDFive.getFileMD5(new File("D:\\api.docx")));
	}

	
	/**
	 * 根据文件计算出文件的MD5
	 * @param file
	 * @return
	 */
	public static String getFileMD5(File file) {
		if (!file.isFile()) {
			return null;
		}
		
		MessageDigest digest = null;
		FileInputStream in = null;
		byte buffer[] = new byte[1024];
		int len;
		try {
			digest = MessageDigest.getInstance("MD5");
			in = new FileInputStream(file);
			while ((len = in.read(buffer, 0, 1024)) != -1) {
				digest.update(buffer, 0, len);
			}
			in.close();

		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		BigInteger bigInt = new BigInteger(1, digest.digest());

		return bigInt.toString(16);
	}
	
	/**
	 * 获取文件夹中的文件的MD5值
	 * @param file
	 * @param listChild
	 * @return
	 */
	public static  Map<String,String> getDirMD5(File file, boolean listChild){
		if(! file.isDirectory()){
			return null;
		}
		
		Map<String, String> map = new HashMap<String, String>();
		String md5;
		
		File[] files = file.listFiles();
		for (int i = 0; i < files.length; i++) {
			File file2 = files[i];
			if(file2.isDirectory() && listChild){
				map.putAll(getDirMD5(file2, listChild));
			}else{
				md5 = getFileMD5(file2);
				if(md5 != null){
					map.put(file2.getPath(), md5);
				}
			}
		}
		return map;
	}

}