JAVA MD5 알고리즘 구현

package tools.com.edu.hdu;
/*
 *           
 *   ：http://en.wikipedia.org/wiki/MD5
 * @Author CCY
 */
public class MD5 {
	/*
	 *       
	 */
	private final int A=0x67452301;
	private final int B=0xefcdab89;
	private final int C=0x98badcfe;
	private final int D=0x10325476;
	/*
	 * ABCD     
	 */
	private int Atemp,Btemp,Ctemp,Dtemp;
	
	/*
	 *   ti
	 *   :floor(abs(sin(i + 1)) × (2 pow 32)
	 */
	private final int K[] = { 
			0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
			0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, 0x698098d8,
			0x8b44f7af, 0xffff5bb1, 0x895cd7be, 0x6b901122, 0xfd987193,
			0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340, 0x265e5a51,
			0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
			0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905,
			0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681,
			0x6d9d6122, 0xfde5380c, 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60,
			0xbebfbc70, 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
			0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, 0xf4292244,
			0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
			0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314,
			0x4e0811a1, 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 };
	/*
	 *      ,      
	 */
	private final int s[] = { 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7,
			12, 17, 22, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
			4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 6, 10,
			15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21 };
	

	/*
	 *      
	 */
	private void init(){
		Atemp=A;
		Btemp=B;
		Ctemp=C;
		Dtemp=D;
	}
	/*
	 *       
	 */
	private int shift(int a,int s){
		return (a<<s)|(a>>>(32-s));//     ，       ，        
	}
	/*
	 *    
	 */
	private void MainLoop(int M[]){
		int F,g;
		int a=Atemp;
		int b=Btemp;
		int c=Ctemp;
		int d=Dtemp;
		for(int i=0;i<64;i++){
			if(i<16){
				F=(b&c)|((~b)&d);
				g=i;
			}
			else if(i<32){
				F=(d&b)|((~d)&c);
				g=(5*i+1)%16;
			}
			else if(i<48){
				F=b^c^d;
				g=(3*i+5)%16;
			}
			else{
				F=c^(b|(~d));
				g=(7*i)%16;
			}
			int tmp=d;
			d=c;
			c=b;
			b=b+shift(a+F+K[i]+M[g],s[i]);
			a=tmp;			
		}
		Atemp=a+Atemp;
		Btemp=b+Btemp;
		Ctemp=c+Ctemp;
		Dtemp=d+Dtemp;
	    
	}
	/*
	 *     
	 *       bits ≡ 448 (mod 512),    bytes ≡ 56（mode64)
	 *          0,     
	 *     64      
	 */
	private int[] add(String str){
		int num=((str.length()+8)/64)+1;// 512 ，64      
		int strByte[]=new int[num*16];//64/4=16，   16   
		for(int i=0;i<num*16;i++){//     0
			strByte[i]=0;
		}
		int i;
		for(i=0;i<str.length();i++){
			strByte[i>>2]|=str.charAt(i)<<((i%4)*8);//          ，   
		}
		strByte[i>>2]|=0x80<<((i%4)*8);//    1
		/*
		 *      ，       ，    8，      ，         ,       32 
		 */
		strByte[num*16-2]=str.length() * 8;
		return strByte;
	}
	/*
	 *     
	 */
	public String getMD5(String source){
		init();
		int strByte[]=add(source);
		for(int i=0;i<strByte.length/16;i+=16){
			int num[]=new int[16];
			for(int j=0;j<16;j++){
				num[j]=strByte[i*16+j];
			}
			MainLoop(num);
		}
		return changeHex(Atemp)+changeHex(Btemp)+changeHex(Ctemp)+changeHex(Dtemp);
		
	}
	/*
	 *     16     
	 */
	private String changeHex(int a){
		String str="";
		for(int i=0;i<4;i++){
			str+=Integer.toHexString(((a>>i*8)%(1<<8))&0xff);
		}
		return str;
	}
	/*
	 *   
	 */
	private static MD5 instance;
	public static MD5 getInstance(){
		if(instance==null){
			instance=new MD5();
		}
		return instance;
	}
	private MD5(){};
}

<pre name="code" class="java">package com.edu.hdu;

import tools.com.edu.hdu.MD5;

public class Test {
	public static void main(String[] args) {
		String str=MD5.getInstance().getMD5("");
		System.out.println(str);
	
	}
}