MyEclipse注册码生成（源码）

package myeclipse;

import java.io.*;

public class MyEclipseGen
{
    private static final String LL = "Decompiling this copyrighted software is a violation of both your license agreement and the Digital Millenium Copyright Act of 1998 (http://www.loc.gov/copyright/legislation/dmca.pdf). Under section 1204 of the DMCA, penalties range up to a $500,000 fine or up to five years imprisonment for a first offense. Think about it; pay for a license, avoid prosecution, and feel better about yourself.";
   
    public String getSerial(String userId, String licenseNum)
    {
        java.util.Calendar cal = java.util.Calendar.getInstance();
        cal.add(1, 3);
        cal.add(6, -1);
        java.text.NumberFormat nf = new java.text.DecimalFormat("000");
        licenseNum = nf.format(Integer.valueOf(licenseNum));
        String verTime = new StringBuilder("-").append(new java.text.SimpleDateFormat(
                "yyMMdd").format(cal.getTime()))
                .append("0")
                .toString();
        String type = "YE3MP-";
        String need = new StringBuilder(userId.substring(0, 1)).append(type)
                .append("300")
                .append(licenseNum)
                .append(verTime)
                .toString();
        String dx = new StringBuilder(need).append(LL)
                .append(userId)
                .toString();
        int suf = this.decode(dx);
        String code = new StringBuilder(need).append(String.valueOf(suf))
                .toString();
        return this.change(code);
    }
   
    private int decode(String s)
    {
        int i;
        char[] ac;
        int j;
        int k;
        i = 0;
        ac = s.toCharArray();
        j = 0;
        k = ac.length;
        while (j < k)
        {
            i = (31 * i) + ac[j];
            j++;
        }
        return Math.abs(i);
    }
   
    private String change(String s)
    {
        byte[] abyte0;
        char[] ac;
        int i;
        int k;
        int j;
        abyte0 = s.getBytes();
        ac = new char[s.length()];
        i = 0;
        k = abyte0.length;
        while (i < k)
        {
            j = abyte0[i];
            if ((j >= 48) && (j <= 57))
            {
                j = (((j - 48) + 5) % 10) + 48;
            }
            else if ((j >= 65) && (j <= 90))
            {
                j = (((j - 65) + 13) % 26) + 65;
            }
            else if ((j >= 97) && (j <= 122))
            {
                j = (((j - 97) + 13) % 26) + 97;
            }
            ac[i] = (char) j;
            i++;
        }
        return String.valueOf(ac);
    }
   
    public MyEclipseGen()
    {
        super();
    }
   
    public static void main(String[] args)
    {
        try
        {
            System.out.println("please input register name:");
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    System.in));
            String userId = null;
            userId = reader.readLine();
            MyEclipseGen myeclipsegen = new MyEclipseGen();
            String res = myeclipsegen.getSerial(userId, "20");
            System.out.println("Serial:" + res);
            reader.readLine();
        }
        catch (IOException ex)
        {
        }
    }
}