generate alphanumeric unique code of variable size using java

//By Milan D Ashara
//Server Side Unique Id Generator
//Use Only If you want to generate Unique ID < 32 Digit else use UID class

import java.util.HashMap;
import java.util.Random;


public class UniqueCode { 
   
   
    static HashMap<Character, Character> map=new HashMap<Character, Character>();
   
    static
    {
        map.put('0', 'A');
        map.put('1', 'Z');
        map.put('2', 'K');
        map.put('3', 'F');
        map.put('4', 'V');
        map.put('5', 'G');
        map.put('6', 'L');
        map.put('7', 'P');
        map.put('8', 'Q');
        map.put('9', 'T');
       
    }
   
    //create Unique Access Code
    /*
     * It can be used to generate unique access code from 13 digit to any number of digits you want
     *
     * */
    private static  StringBuilder createUniqueAccessCode(int aStart, long aEnd, Random aRandom) throws Exception{
        if ( aStart > aEnd ) {
          throw new IllegalArgumentException("Start cannot exceed End.");
        }
        StringBuilder accCode=new StringBuilder();
        //get the range, casting to long to avoid overflow problems
        long range = aEnd - (long)aStart + 1;
        System.out.println("range>>>>>>>>>>>"+range);
        // compute a fraction of the range, 0 <= frac < range
        long fraction = (long)(range * aRandom.nextDouble());
    //    System.out.println("fraction>>>>>>>>>>>>>>>>>>>>"+fraction);
        long randomNumber =  fraction + (long)aStart;
       
        accCode.append(randomNumber); //generate code in range of start and end
        accCode.append(System.currentTimeMillis()); //generate 13 digit code
       
        Thread.sleep(10);
      
        //replace certain characters with alphabet
       
        accCode.replace(4, 4, map.get(accCode.charAt(4)).toString());
        accCode.deleteCharAt(5);
        accCode.replace(1, 1, map.get(accCode.charAt(1)).toString());
        accCode.deleteCharAt(2);
        accCode.replace(3, 3, map.get(accCode.charAt(3)).toString());
        accCode.deleteCharAt(4);
        accCode.replace(6, 6, map.get(accCode.charAt(6)).toString());
        accCode.deleteCharAt(7);
        accCode.replace(11, 11, map.get(accCode.charAt(11)).toString());
        accCode.deleteCharAt(12);
        accCode.replace(13, 13, map.get(accCode.charAt(13)).toString());
        accCode.deleteCharAt(14);
        accCode.replace(14, 14, map.get(accCode.charAt(14)).toString());
        accCode.deleteCharAt(15);
        accCode.replace(15, 15, map.get(accCode.charAt(15)).toString());
        accCode.deleteCharAt(16);
        accCode.insert(4, '-');
        accCode.insert(9, '-');
        
        System.out.println("Generated : " + accCode.toString());
        return accCode;
       
      }

   
    //test create 16 digit unique Id
 public static void main(String[] args) throws Exception
 { 

   
   
     // example to generate 16 digit unique code
      for(int i=0;i<100;i++)   
          createUniqueAccessCode(100, 999L, new Random());

 } 
}