Java 集合 ArrayList排序

import java.util.*;
public class Details  {

    public static void main(String args[]){
       ArrayList<String> listofcountries = new ArrayList<String>();
       listofcountries.add("India");
       listofcountries.add("US");
       listofcountries.add("China");
       listofcountries.add("Denmark");

       /*Unsorted List*/
       System.out.println("Before Sorting:");
       for(String counter: listofcountries){
            System.out.println(counter);
        }

       /* Sort statement*/
       Collections.sort(listofcountries);

       /* Sorted List*/
       System.out.println("After Sorting:");
       for(String counter: listofcountries){
            System.out.println(counter);
        }
    }
}

Before Sorting:
India
US
China
Denmark
After Sorting:
China
Denmark
India
US

import java.util.*;
public class ArrayListOfInteger  {

    public static void main(String args[]){
       ArrayList<Integer> arraylist = new ArrayList<Integer>();
       arraylist.add(11);
       arraylist.add(2);
       arraylist.add(7);
       arraylist.add(3);
       /* ArrayList before the sorting*/
       System.out.println("Before Sorting:");
       for(int counter: arraylist){
            System.out.println(counter);
        }

       /* Sorting of arraylist using Collections.sort*/
       Collections.sort(arraylist);

       /* ArrayList after sorting*/
       System.out.println("After Sorting:");
       for(int counter: arraylist){
            System.out.println(counter);
        }
    }
}

Before Sorting:
11
2
7
3
After Sorting:
2
3
7
11