newstringmd5.java

这是一个获取文件MD5码的JAVA程序。可以用于学习JAVA

package com.md5.chen;

import org.apache.commons.codec.binary.Base64;

import java.io.*;
import java.security.DigestInputStream;
import java.security.MessageDigest;

//获取BASE64编码的字符串MD5
public class NewStringMD5
{
	public static byte[] encode(byte[] buf)
	{
		if (buf == null)
		{
			return encode(buf, 0, 0);
		} else
		{
			return encode(buf, 0, buf.length);
		}
	}

	// 将 buf 进行 BASE64 编码
	public static byte[] encode(byte[] buf, int pos, int length)
	{
		byte[] result = null;

		if (length > 0)
		{
			if (pos == 0 && buf.length == length)
			{
				return Base64.encodeBase64(buf);
			} else
			{
				byte[] newbuf = new byte[length];
				System.arraycopy(buf, pos, newbuf, 0, length);
				result = Base64.encodeBase64(newbuf);
			}
		}
		return result;
	}

	// 将 BASE64 编码的字符串 buf 进行解码
	public static byte[] decode(byte[] buf, int pos, int length)
			throws IOException
	{
		byte[] result = null;

		if (length > 0)
		{
			result = FastBase64.decodeBase64(buf, pos, length);

			// if (pos == 0 && buf.length == length) {
			// result = Base64.decodeBase64(buf);
			// } else {
			// byte[] newbuf = new byte[length];
			// System.arraycopy(buf, pos, newbuf, 0, length);
			// result = Base64.decodeBase64(newbuf);
			// }
		}

		return result;
	}
	
	public static void main(String[] args)throws Exception 
	{
		String t = "A";
		String  md5String = "";
		// 为一个字符串计算MD5
		try
		{
			// 生成MessageDigest对象MD
			MessageDigest MD = MessageDigest.getInstance("MD5");
		    // 传入要计算的字符串
			MD.update(t.getBytes("UTF-8"));
			// 计算MD5
			 md5String = new String(encode(MD.digest()));

		} catch (Exception e)
		{
			System.out.println(e.getMessage());
		}
		System.out.println("字符串 "+t+" 的BASE64编码的MD5:" + md5String);
       
		/*
		String tt="QQ==";
		
		byte[] decodeByte= decode(tt.getBytes(),0,tt.length());
		
		System.out.println("length:"+decodeByte.length);
		//String decodeString = new String(decode(tt.getBytes(),0,tt.length()));
	   // System.out.println("解码后:"+decodeString);
		for(int i=0;i<decodeByte.length;i++)
		{
			System.out.print(decodeByte[i]); 
		}
		*/
		
		
	}

}