java 文件md5+字符串md5 实现

import org.apache.commons.codec.binary.Hex;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.log4j.Logger;

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

/**
* md5算法工具
*/
public class MD5BigFileUtil {
private final static Logger logger = Logger.getLogger(MD5BigFileUtil.class);
static MessageDigest md = null;

static {
try {
md = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException ne) {
logger.error("NoSuchAlgorithmException: md5", ne);
}
}

/**
* 对一个文件求他的md5值
* @param f 要求md5值的文件
* @return md5串
*/
public static String md5(File f) {
FileInputStream fis = null;
try {
fis = new FileInputStream(f);
//100KB each time
byte[] buffer = new byte[102400];
int length;
long loopCount = 0;
while ((length = fis.read(buffer)) != -1) {
md.update(buffer, 0, length);
loopCount++;
}

logger.debug("read file to buffer loopCount:"+loopCount);

return new String(Hex.encodeHex(md.digest()));
} catch (FileNotFoundException e) {
logger.error("md5 file " + f.getAbsolutePath() + " failed:" + e.getMessage());
return null;
} catch (IOException e) {
logger.error("md5 file " + f.getAbsolutePath() + " failed:" + e.getMessage());
return null;
} finally {
try {
if (fis != null) fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

/**
* 求一个字符串的md5值
* @param target 字符串
* @return md5 value
*/
public static String md5(String target) {
return DigestUtils.md5Hex(target);
}

public static void main(String[] args) {
long begin =System.currentTimeMillis();
System.out.println(md5(new File("G:/BT/PremierePro_6_LS7.7z")));
long end =System.currentTimeMillis();
System.out.println("time:"+((end-begin)/1000)+"s");

System.out.println(md5("hello world"));
}

}