java入门第三季 6-5 sort作业

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

public class Sort {
    public void testSort1() {
        ArrayList<Integer> list1 = new ArrayList<Integer>();
        Random random = new Random();
        int x = 0;
        for (int i = 0; i < 10; i++) {
            do {
                x = random.nextInt(100);
            } while (list1.contains(x));
            list1.add(x);
        }
        System.out.println("排序前");
        for (Integer integer : list1) {
            System.out.println(integer);
        }
        System.out.println("排序后");
        Collections.sort(list1);
        for (Integer integer : list1) {
            System.out.println(integer);
        }
    }
    public void test02() {
        ArrayList<String> list2=new ArrayList<String>();
        list2.add("wasdasd");
        list2.add("addwwd");
        list2.add("dddddw");
        list2.add("saa");
        System.out.println("排序前");
        for (String string : list2) {
            System.out.println(string);
        }
        System.out.println("排序后");
        Collections.sort(list2);
        for (String string : list2) {
            System.out.println(string);
        }
    }
    public void test03() {
        //存储长度为10的字符串集
        ArrayList<String> list3=new ArrayList<String>();
        //从中随机抽取字符
        String string="0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
        //随机数
        Random random=new Random();
        //添加20个字符串
        for(int i=0;i<20;i++){
            //用来存储字符串
            StringBuilder stringBuilder=new StringBuilder();
            //每个字符串长度为10
            for(int j=0;j<10;j++){
                //1.里面的语句string.charAt() 返回指定索引处的char值
                //2.random.nextInt(string.length()-1)  括号内是指定随机数的取值范围 字符串的长度-1 就是这个数组的最大索引
                //也就是说 2.返回一个值  让 1. 可以获得一个char值  
                stringBuilder.append(string.charAt(random.nextInt(string.length()-1)));
            }
            //添加进集合
            list3.add(stringBuilder.toString());
        }
        System.out.println("排序前");
        for (String string2 : list3) {
            System.out.println(string2);
        }
        System.out.println("排序后");
        Collections.sort(list3);
        for (String string2 : list3) {
            System.out.println(string2);
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Sort sort=new Sort();
        sort.test03();
    }

}