对随机产生的10个字符串进行排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class sortString {

    public void testSort2_0(){
        List<String> st = new ArrayList<String>();
        Random random =new Random();
        String s="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        for (int i = 0; i < 10; i++) {
            StringBuilder temp = new StringBuilder("");//存储临时产生的字符串
            do{
                int k = random.nextInt(9)+1;//保存随机字符串的长度
                for (int j = 0; j < k; j++) {
                    int a = random.nextInt(s.length());//从s中取出一个随机字符
                    temp.append(s.charAt(a));//将取出的字符添加到存储临时字符串的末尾
                }
                System.out.println("将要添加的字符串" + "'"+temp+"'");
            }while(st.contains(temp.toString()));//判断得到的字符串是否重复
            st.add(temp.toString());            //重复继续循环取字符串，不重复则将其添加到list中
        }
        System.out.println("-------排序前-------------");
        for (String string : st) {
            System.out.println("字符串为:"+ string);
        }
        Collections.sort(st);//对list排序
        System.out.println("-------排序后-------------");
        for (String string : st) {
            System.out.println("字符串为:"+ string);
        }

    } 

    public static void main(String[] args) {
        sortString test = new sortString();
        test.testSort2_0();
    }

}