获取随机字符串并对其进行排序

package stringsort;

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

public class stringsort {
public void test(){
List<String> list=new ArrayList();
String str3;
for(int i=0;i<10;i++){
do{
str3=random(10);
}while(list.contains(str3));
list.add(random(10));
}
System.out.println("---------排序前-----------");
for (String string : list) {
System.out.println("元素:"+string);
}
Collections.sort(list);
System.out.println("---------排序后-----------");
for (String string : list) {
System.out.println("元素:"+string);
}

}
public String random(int length){
    String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    Random random=new Random();
    StringBuffer str1=new StringBuffer();
    for(int i=0;i<length;i++){
        int num=random.nextInt(62);
        str1.append(str.charAt(num));
    }
    return str1.toString();
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    stringsort str2=new stringsort();
    str2.test();

}

}