importjava.io.FileInputStream;importjava.security.DigestInputStream;importjava.security.MessageDigest;importjava.security.NoSuchAlgorithmException;public classMD5Class {//计算字符串的MD5

public staticString conVertTextToMD5(String plainText) {try{

MessageDigest md= MessageDigest.getInstance("MD5");

md.update(plainText.getBytes());byte b[] =md.digest();inti;

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));

}//32位加密

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

} catch(NoSuchAlgorithmException e) {

e.printStackTrace();return null;

}

}

//计算文件的MD5，支持4G一下的文件(文件亲测，大文件未亲测)public staticString conVertFileToMD5(String inputFilePath) {int bufferSize = 256 * 1024;

FileInputStream fileInputStream= null;

DigestInputStream digestInputStream= null;try{//拿到一个MD5转换器(同样，这里可以换成SHA1)

MessageDigest messageDigest= MessageDigest.getInstance("MD5");//使用DigestInputStream

fileInputStream= newFileInputStream(inputFilePath);

digestInputStream= newDigestInputStream(fileInputStream,

messageDigest);//read的过程中进行MD5处理，直到读完文件

byte[] buffer = new byte[bufferSize];while (digestInputStream.read(buffer) > 0)

;//获取最终的MessageDigest

messageDigest=digestInputStream.getMessageDigest();//拿到结果，也是字节数组，包含16个元素

byte[] resultByteArray =messageDigest.digest();//同样，把字节数组转换成字符串

returnbyteArrayToHex(resultByteArray);

}catch(Exception e) {return null;

}finally{try{

digestInputStream.close();

}catch(Exception e) {

}try{

fileInputStream.close();

}catch(Exception e) {

}

}

}private static String byteArrayToHex(byte[] byteArray) {//首先初始化一个字符数组，用来存放每个16进制字符

char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9','A', 'B', 'C', 'D', 'E', 'F'};//new一个字符数组，这个就是用来组成结果字符串的(解释一下：一个byte是八位二进制，也就是2位十六进制字符(2的8次方等于16的2次方))

char[] resultCharArray = new char[byteArray.length * 2];//遍历字节数组，通过位运算(位运算效率高)，转换成字符放到字符数组中去

int index = 0;for (byteb : byteArray) {

resultCharArray[index++] = hexDigits[b >>> 4 & 0xf];

resultCharArray[index++] = hexDigits[b & 0xf];

}//字符数组组合成字符串返回

return newString(resultCharArray);

}public static voidmain(String[] args) {//测试

System.out.println(MD5Class.conVertTextToMD5("hello"));

System.out

.println(conVertFileToMD5("C:\\Users\\administrator1\\Downloads\\StarUML-v2.8.0.msi"));

}

}