How to sort Arraylist in Java with Example

By default, the ArrayList’s elements are display according to the sequence it is put inside. Often times, you may need to sort the ArrayList to make it alphabetically order. In this example, it shows the use of Collections.sort(‘List’) to sort an ArrayList.

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

public class SortArrayList{

        public static void main(String args[]){

                List<String> unsortList = new ArrayList<String>();

                unsortList.add("CCC");
                unsortList.add("111");
                unsortList.add("AAA");
                unsortList.add("BBB");
                unsortList.add("ccc");
                unsortList.add("bbb");
                unsortList.add("aaa");
                unsortList.add("333");
                unsortList.add("222");

                //before sort
                System.out.println("ArrayList is unsort");
                for(String temp: unsortList){
                        System.out.println(temp);
                }

                //sort the list
                Collections.sort(unsortList);

                //after sorted
                System.out.println("ArrayList is sorted");
                for(String temp: unsortList){
                        System.out.println(temp);
                }
        }

}
Output
ArrayList is unsort
CCC
111
AAA
BBB
ccc
bbb
aaa
333
222
ArrayList is sorted
111
222
333
AAA
BBB
CCC
aaa
bbb
ccc

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Posted in: Java Question