JAVA集合生成10条随机字符串排序

package cn.edu.lin.task;

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

/**
 * Created by asus on 2016/11/4.
 */
public class CollectionsTask {

    public static List<String> listRandomString() {
        String str = "qwertyuiopasdfghjklzxcvbnmQWERRTYUIOPASDFGHJKLZXCVBNM1234567890";
        Random random = new Random();
        List<String> listString = new ArrayList<String>();
        String[] strArray = new String[10];
        for (int i = 0; i < 10; i++) {
            StringBuffer stringBuffer = new StringBuffer();
            //确定字符串长度
            int size = (int) (Math.random() * 10);
            for (int j = 0; j < size; j++) {
                int index = random.nextInt(str.length());
                char c = str.charAt(index);
                stringBuffer.append(c);
            }
            if (!(listString.contains(stringBuffer.toString()))) {
                listString.add(stringBuffer.toString());
            } else {
                i--;
            }

        }
        return listString;
    }

    public static void main(String[] args){
          List<String > strList = listRandomString();
        System.out.println("--------生成10条随机字符串--------");
        for(String string  : strList){
            System.out.println(string);
        }
        System.out.println("--------排序后-------------");
        Collections.sort(strList);
        for(String string :strList){
            System.out.println(string);
        }
    }
}