MyEclipse注册码生成

package com;
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) { 
            } 
        } 
    }