import javax.swing.*;
import java.util.ArrayList;
import java.util.Random;
public class TestRandom {
    private static Random random = new Random();
    private static final int length = 8;
    private static String value = "a-zA-Z0-9";
    private static ArrayList lower = null;
    private static ArrayList upper = null;


public static void main(String[] args)
 {
  getRandom();
 }
 
    private static final float getFloat() {
         return random.nextFloat();
        }
    
    private static final String getRandom(){
  TestRandom thisc = new TestRandom();
  thisc.setCharset();
  String randomstr = "";
  try {
   //建立一個random字符串
   for (int i = 0; i < length; i++) {
       // 取得隨機偶數和隨機奇數
       if (((int) (getFloat() * 100)) % 2 == 0) {
       randomstr = randomstr + randomChar((Character)lower.get(2),(Character)upper.get(2)).toString();

       } else {
            if (((int) (getFloat() * 100)) % 2 == 0)  {
              randomstr = randomstr + randomChar((Character)lower.get(1),(Character)upper.get(1)).toString();
           } else
             randomstr = randomstr + randomChar((Character)lower.get(0),(Character)upper.get(0)).toString();
           }
       }
   
   System.out.println(randomstr);

  }   catch(Exception e)  {
   e.printStackTrace();
  }
  return randomstr;
    }
    
    private static final Character randomChar(Character lower, Character upper) {
     int tempval;
     char low = lower.charValue();
     char up = upper.charValue();
     
     tempval = (int)((int)low + (getFloat() * ((int)(up - low))));

     return (new Character((char) tempval));
        }
    
    public final void setCharset() 
    {
     System.out.println("start setCharset ...");
    boolean more = true;
    
    lower = new ArrayList(3);
    upper = new ArrayList(3);
   if ((value.charAt(1) == '-') && (value.charAt(0) != '\\')) {

     while (more && (value.charAt(1) == '-')){

         if (value.charAt(0) == '\\')
             break;
        else {
         
         lower.add(new Character(value.charAt(0)));
         upper.add(new Character(value.charAt(2)));
        }

      if (value.length() <= 3) {
            more = false;
      }else{
         value = value.substring(3);
      }
    }
  }
    if ((lower == null))
     setCharset(); 
}
}