隨機產生20個字符串並且字符串不能重複 且進行排序

package com.test.kaoshi;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;
import java.util.Set;
import java.util.TreeSet;

public class RadomDemo {
/**
 * 隨機產生20個字符串並且字符串不能重複 且進行排序
 * @param random
 * @param len
 * @return
 */
    public Set getChar(){

        Set numberSet01 = new HashSet();
        Random rdm = new Random();
        char ch;
        while(numberSet01.size()<20){
           int rdGet = Math.abs(rdm.nextInt())%26+97;//產生97到122的隨機數a-z值
            ch=(char)rdGet;
            numberSet01.add(ch);
            //Set中是不能放進重複的值的，當它有20個時，就滿足你的條件了
        }
          return numberSet01;
        }
    public static void main(String[] args) {
        RadomDemo rd = new RadomDemo();
        Set numberSet01=rd.getChar();

        Set numberSet = new TreeSet();
        numberSet.addAll(numberSet01);
        for(Iterator it=numberSet01.iterator();it.hasNext();){
            System.out.print(it.next());
            }
        System.out.println();
        for(Iterator it=numberSet.iterator();it.hasNext();){
            System.out.print(it.next());
            }
    }
}