- Given an arraylist collection of String objects in java.
- We would like to retain certain elements of arraylist (and would like to remove rest of elements of arraylist).
- Arraylist has following method to retain elements.
- boolean retainAll(Collection<?> c)
- Retains only the elements in this list that are contained in the specified collection.
- boolean retainAll(Collection<?> c)
- We will create array list containing number of sports.
- OrignalArrayList:[archery, badminton, canoe, boxing, diving, beach volleyball]
- We would like to retain elements in original array list, which are present in retainSportsList.
- e.g. retainSportsList: [soccer, judo, archery, badminton]
- The output of OrignalArrayList.retainAll(retainSportsList) should return [archery, badminton]
- i.e. All elements of retainSportsList will be retained in OrignalArrayList (if present in OriginalArrayList).
1. Retain/remove String objects/elements of arraylist collection in java
package org.learn.collection.list.arrayList; import java.util.ArrayList; public class DemoRetainInOfArrayList { public static void main(String[] args) { ArrayList<String> arrayList = new ArrayList<>(); arrayList.add( "archery" ); arrayList.add( "badminton" ); arrayList.add( "canoe" ); arrayList.add( "boxing" ); arrayList.add( "diving" ); arrayList.add( "beach volleyball" ); System.out.println( "Demo of retain method: " ); demoRetainAll(arrayList); } private static void demoRetainAll(ArrayList<String> arrayList) { System.out.println( "1. Orignal ArrayList:" + arrayList); ArrayList<String> retainSportsList = new ArrayList<>(); retainSportsList.add( "soccer" ); retainSportsList.add( "judo" ); retainSportsList.add( "archery" ); retainSportsList.add( "badminton" ); System.out.println( "2. Elements in retainSportsList:" +retainSportsList); arrayList.retainAll(retainSportsList); //What ever element presents in source list, will be retained. System.out.println( "3. Retained elements in arraylist: " + arrayList); } } |
2. Retain/remove String objects/elements of arraylist collection (example)
Demo of retain method: 1. Orignal ArrayList:[archery, badminton, canoe, boxing, diving, beach volleyball] 2. Elements in retainSportsList:[soccer, judo, archery, badminton] 3. Retained elements in arraylist: [archery, badminton] |