java实现MD5加密解密

这里第一种是在网上看的比较好，拿来使用。下面有第二个，个人感觉第二个使用比较方便，而且容易理解！

注意：这里无论是第一种还是第二种，运行一次为加密，运行两次是进行解密！！！！

第一种：

import java.io.UnsupportedEncodingException;  
import java.security.MessageDigest;  `在这里插入代码片`
import java.security.NoSuchAlgorithmException;  
  
/** 
 * 采用MD5加密解密 
 * @author tfq 
 * @datetime 2011-10-13 
 */  
public class MD5Util {  
  
    /*** 
     * MD5加码 生成32位md5码 
     */  
    public static String string2MD5(String inStr){  
        MessageDigest md5 = null;  
        try{  
            md5 = MessageDigest.getInstance("MD5");  
        }catch (Exception e){  
            System.out.println(e.toString());  
            e.printStackTrace();  
            return "";  
        }  
        char[] charArray = inStr.toCharArray();  
        byte[] byteArray = new byte[charArray.length];  
  
        for (int i = 0; i < charArray.length; i++)  
            byteArray[i] = (byte) charArray[i];  
        byte[] md5Bytes = md5.digest(byteArray);  
        StringBuffer hexValue = new StringBuffer();  
        for (int i = 0; i < md5Bytes.length; i++){  
            int val = ((int) md5Bytes[i]) & 0xff;  
            if (val < 16)  
                hexValue.append("0");  
            hexValue.append(Integer.toHexString(val));  
        }  
        return hexValue.toString();  
  
    }  
  
    /** 
     * 加密解密算法 执行一次加密，两次解密 
     */   
    public static String convertMD5(String inStr){  
  
        char[] a = inStr.toCharArray();  
        for (int i = 0; i < a.length; i++){  
            a[i] = (char) (a[i] ^ 't');  
        }  
        String s = new String(a);  
        return s;  
  
    }  
  
    // 测试主函数  
    public static void main(String args[]) {  
        String s = new String("tangfuqiang");  
        System.out.println("原始：" + s);  
        System.out.println("MD5后：" + string2MD5(s));  
        System.out.println("加密的：" + convertMD5(s));  
        System.out.println("解密的：" + convertMD5(convertMD5(s)));  
  
    }  
} 

第二种：

import java.security.MessageDigest;



public class MD5 {
	 private static final String hexDigIts[] = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};

	  
	    public  String MD5Encode(String origin, String charsetname){
	        String resultString = null;
	        try{
	            resultString = new String(origin);
	            MessageDigest md = MessageDigest.getInstance("MD5");
	            if(null == charsetname || "".equals(charsetname)){
	                resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
	            }else{
	                resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
	            }
	        }catch (Exception e){
	        }
	        return resultString;
	    }

	    
	    public  String byteArrayToHexString(byte b[]){
	        StringBuffer resultSb = new StringBuffer();
	        for(int i = 0; i < b.length; i++){
	            resultSb.append(byteToHexString(b[i]));
	        }
	        return resultSb.toString();
	    }
	    
	    public  String byteToHexString(byte b){
	        int n = b;
	        if(n < 0){
	            n += 256;
	        }
	        int d1 = n / 16;
	        int d2 = n % 16;
	        return hexDigIts[d1] + hexDigIts[d2];
	    }
	    
//	    public static void main(String[] args) {
//	    	String password = "12345";
//	    	String password2 = new Test().MD5Encode(password,"utf8");
//	    	System.out.println(password+"\t"+password2);
//	    	
//	    	String a = "12345";
//	    	String b = new Test().MD5Encode(a,"utf8");
//	    
//	    	System.out.println(password2.equals(b));
//		}

}