Java 生成MD5

MD5（Message Digest Algorithm），消息摘要算法，一般用于校验文件的完整性。Java内置已经实现了MD5，与SHA1算法,利用java.security.MessageDigest类就可以获取文件/字符串的MD5或SHA1

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.security.DigestInputStream;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

public class MD5AndSHA1Helper {

	/**

	 * 将字节数组转换为16进制字符串

	 * @param resultArr

	 * @return 16进制字符串

	 */

	private static String byteArrToHex(byte[] byteArr) {

		// Initialize the character array, used to store each hexadecimal string

		char[] hexDigits = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

		// Initialize a char Array, used to form the result string

		char[] resultCharArr = new char[byteArr.length*2];

		// Traverse the byte array, converted into characters in a character array

		int index = 0;

		for (byte b : byteArr) {

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

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

		}

		return new String(resultCharArr);

	}

	/**

	 * 获取字符串的MD5

	 * @param input

	 * @return

	 */

	public static String getStringMD5(String input){

		try {

			// get MD5 digest

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

			// The input String to Byte Array

			byte[] inputArr = input.getBytes();

			// Updates the digest using the specified byte.

			mDigest.update(inputArr);

			// Completes the hash computation by performing final operations such as padding.

			// The digest is reset after this call is made.

			byte[] resultArr = mDigest.digest();

			//

			return byteArrToHex(resultArr);

		} catch (NoSuchAlgorithmException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		return null;

	}

	/**

	 * 获取文件的MD5，可以替换为SHA1

	 * @param inputFile

	 * @return

	 * @throws IOException

	 */

	@SuppressWarnings("resource")

	public static String getFileMD5(String fileUrl) throws IOException{

		int bufferSize = 1024*1024;

		FileInputStream fileInputStream = null;

		DigestInputStream digestInputStream = null;

		try {

			// 可以替换为"SHA1"

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

			fileInputStream = new FileInputStream(fileUrl);

			// Creates a digest input stream, using the specified input stream and message digest.

			digestInputStream = new DigestInputStream(fileInputStream, mDigest);

			byte[] buffer = new byte[bufferSize];

			while(digestInputStream.read(buffer)>0);

			mDigest = digestInputStream.getMessageDigest();

			byte[] resultArr = mDigest.digest();

			return byteArrToHex(resultArr);

		} catch (NoSuchAlgorithmException e) {

			e.printStackTrace();

		}finally{

			fileInputStream.close();

			digestInputStream.close();

		}

		return null;

	}

	/**

	 * 获取String的SHA1

	 * @param input

	 * @return

	 */

	public static String getStringSHA1(String input){

		try {

			MessageDigest mDigest = MessageDigest.getInstance("SHA1");

			byte[] inputArr = input.getBytes();

			mDigest.update(inputArr);

			byte[] resultArr = mDigest.digest();

			return byteArrToHex(resultArr);

		} catch (NoSuchAlgorithmException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		return null;

	}

	public static void main(String[] args) {

//		String result = MD5AndSHA1Helper.getStringMD5("111");

//		String result = MD5AndSHA1Helper.getStringSHA1("1111");

		String path = "/Users/Dream_Kidd/Downloads/wanda19environment-x64/apache-tomcat-7.0.62-windows-x64.zip";

		String result;

		try {

			result = MD5AndSHA1Helper.getFileMD5(path);

			System.out.println(result);

		} catch (IOException e) {

			e.printStackTrace();

		}

	}

}

建议，如果过G的文件，不建议使用Java自带的MD5