6-5课后练习题答案详解

package com.imooc.collection;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class collectiontest {

//随机生成字符串
public static String getRandomString(int length) {
    //length表示生成字符串的长度    
    String base = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";       
    Random random = new Random();       
    StringBuffer sb = new StringBuffer();       
    for (int i = 0; i < length; i++) {       
        int number = random.nextInt(base.length());       
        sb.append(base.charAt(number));       
    }       
    return sb.toString();       
 }  
public static void main(String[] args) {
        // TODO Auto-generated method stub
        String  b = null;
        List<String> a=new ArrayList<String>();
        Random random=new Random();
        collectiontest ct=new collectiontest();
        for(int i=0;i<10;i++)
        {Integer k=random.nextInt(10);
         do{ b=collectiontest.getRandomString(k);}while(a.contains(b));
        a.add(b);}
        Collections.sort(a);
        System.out.println("排序后");
        for(String c:a){System.out.println("元素"+c);}}
        }