Java哈希散列算法简介 - MD5 & SHA-512

package com.andycbluo.secure.checksum.util;

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

public class SecureUtil {
    
    private final String SHA512 = "SHA-512";
    private static SecureUtil _instance = null;
    
    private SecureUtil() {}
    
    /**
     * 
     * @return
     */
    public static SecureUtil getInstance() {
        return _instance;
    }
    
    /**
     * 
     * @param data
     * @return
     */
    public String generateChecksum(String data) {
        return generateChecksum(data, SHA512);
    }
    
    /**
     * 
     * @param data
     * @param algorithom
     * @return
     */
    public String generateChecksum(String data, String algorithom) {
        String checksum = null;
        
        try {
            MessageDigest instance = MessageDigest.getInstance(algorithom);
            instance.update(data.getBytes("UTF-8"));
            checksum = convertBytes2String(instance.digest());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        
        return checksum;
    }
    
    /**
     * 
     * @param data
     * @return
     */
    private String convertBytes2String(byte[] data) {
        StringBuffer sb = new StringBuffer();
        for(int i = 0; i < data.length; i++) {
            sb.append(Integer.toString(data[i] & 0xFF + 0x100, 16).substring(1));
        }
        
        return sb.toString();
    }
    
    /**
     * 
     * @param filePath
     * @return
     */
    public String generateFileChecksum(String filePath) {
        return generateFileChecksum(filePath, SHA512);
    }
    
    /**
     * 
     * @param filePath
     * @param algorithom
     * @return
     */
    public String generateFileChecksum(String filePath, String algorithom) {
        String checksum = null;
        
        MessageDigest instance;
        try {
            instance = MessageDigest.getInstance(algorithom);
            
            InputStream fis = new FileInputStream(new File(filePath));
            
            byte[] blob = new byte[1024];
            int numRead;
            do {
                numRead = fis.read(blob);
                if (numRead > 0) {
                    instance.update(blob, 0, numRead);
                }
            } while (numRead != -1);
            
            checksum = convertBytes2String(instance.digest());
            
            fis.close();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        return checksum;
    }
    
    /**
     * 
     */
    static {
        _instance = new SecureUtil();
    }
}

package com.andycbluo.secure.checksum;

import com.andycbluo.secure.checksum.util.SecureUtil;

public class TestRunner {
    private static final String TEST_DATA = "This is a testing data : 123456789";
    private static final String FILE_PATH = "<Replace Your File Path Name Here>";
    
    public static void main(String[] args) {
        System.out.println("SHA-512 : " + SecureUtil.getInstance().generateChecksum(TEST_DATA));
        System.out.println("MD5 : " + SecureUtil.getInstance().generateChecksum(TEST_DATA, "MD5"));
        
        System.out.println("File SHA-512 : " + SecureUtil.getInstance().generateFileChecksum(FILE_PATH));
        System.out.println("File MD5 : " + SecureUtil.getInstance().generateFileChecksum(FILE_PATH, "MD5"));
    }
}