Java Map equals() Method

List retainAll() Method in Java with Examples

Last Updated : 02 Jan, 2019

This method is used to retain all the elements present in the collection from the specified collection into the list.

Syntax:

boolean retainAll(Collection c)

Parameters: This method has only argument, collection of which elements are to be retained in the given list.

Returns: This method returns True if elements are retained and list changes.

Below programs show the implementation of this method.

Program 1:

// Java code to show the implementation of 
// retainAll method in list interface 
import java.util.*; 
public class GfG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Initializing a list of type Linkedlist 
        List<Integer> l = new LinkedList<>(); 
        l.add(1); 
        l.add(3); 
        l.add(5); 
        l.add(7); 
        l.add(9); 
        System.out.println(l); 
  
        ArrayList<Integer> arr = new ArrayList<>(); 
        arr.add(3); 
        arr.add(5); 
        l.retainAll(arr); 
  
        System.out.println(l); 
    } 
} 

Output:

[1, 3, 5, 7, 9]
[3, 5]

Program 2: Below is the code to show implementation of list.retainAll() using Linkedlist.

// Java code to show the implementation of 
// retainAll method in list interface 
import java.util.*; 
public class GfG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Initializing a list of type Linkedlist 
        List<String> l = new LinkedList<>(); 
        l.add("10"); 
        l.add("30"); 
        l.add("50"); 
        l.add("70"); 
        l.add("90"); 
        System.out.println(l); 
  
        ArrayList<String> arr = new ArrayList<>(); 
        arr.add("30"); 
        arr.add("50"); 
        l.retainAll(arr); 
  
        System.out.println(l); 
    } 
} 

Output:

[10, 30, 50, 70, 90]
[30, 50]

Reference:
Oracle Docs

Java Map equals() Method

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