Java MD5 String md5(String data)

Description

Hashes a String using the MD5 algorithm and returns the result as a String of hexadecimal numbers.

License

Apache License

Declaration

public static String md5(String data) 

Method Source Code

//package com.java2s;
/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.//  ww  w.  j  a  v a 2 s.c  om
 */

import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Main {
    public static final String MD5 = "MD5";

    /** 
     * Hashes a String using the MD5 algorithm and returns the result as a
     * String of hexadecimal numbers.
     */
    public static String md5(String data) {
        return hash(data, MD5);
    }

    /** 
     * Hashes a byte array using the MD5 algorithm and returns the result as a
     * String of hexadecimal numbers.
     */
    public static String md5(byte[] data) {
        return hash(data, MD5);
    }

    /** 
     * Hashes an InputStream using the MD5 algorithm and returns the result as 
     * a String of hexadecimal numbers.
     */
    public static String md5(InputStream in) throws IOException {
        return hash(in, MD5);
    }

    /**
     * Hashes a String using the specified algorithm and returns the result as 
     * a String of hexadecimal numbers.
     * 
     * @param data the String to compute the hash of
     * @return the computed hash
     */
    public static String hash(String data, String algorithm) {
        return hash(data.getBytes(), algorithm);
    }

    /**
     * Hashes a byte array using the specified algorithm and returns the 
     * result as a String of hexadecimal numbers.
     * 
     * @param data the bytes to compute the hash of
     * @return the computed hash
     */
    public static String hash(byte[] data, String algorithm) {
        MessageDigest digest = createDigest(algorithm);
        digest.update(data);
        return toHex(digest.digest());
    }

    /**
     * Hashes data read from an InputStream using the specified algorithm 
     * and returns the result as a String of hexadecimal numbers.
     * 
     * @param in the stream to read the data from
     * @return the computed hash
     */
    public static String hash(InputStream in, String algorithm) throws IOException {

        MessageDigest digest = createDigest(algorithm);
        byte[] buffer = new byte[8192];
        int i = 0;
        while ((i = in.read(buffer)) > 0) {
            digest.update(buffer, 0, i);
        }
        in.close();
        return toHex(digest.digest());
    }

    /**
     * Creates a MessageDigest for the given algorithm. 
     * NoSuchAlgorithmExceptions are caught and re-thrown as RuntimeExceptions.
     */
    private static MessageDigest createDigest(String algorithm) {
        try {
            return MessageDigest.getInstance(algorithm);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Converts an array of bytes into a String representing each byte as an
     * unsigned hex number.
     * 
     * @param buffer array of bytes to convert
     * @return generated hex string
     */
    private static String toHex(byte[] buffer) {
        StringBuffer sb = new StringBuffer();
        String s = null;
        for (int i = 0; i < buffer.length; i++) {
            s = Integer.toHexString((int) buffer[i] & 0xff);
            if (s.length() < 2) {
                sb.append('0');
            }
            sb.append(s);
        }
        return sb.toString();
    }
}

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