retainAll() method explanation with HashSet

In this article, we will discuss retainAll() method of Collection interface with HashSet

 

boolean retainAll(Collection c); remove/deletes all element/objects of invoking collection except specified collection

(i.e.; retaining specified collection and removing other objects from invoking collection)

 

retainAll() method of Collection interface

RetainAllMethodWithHashSet.java

package in.bench.resources.java.collections;

import java.util.HashSet;

public class RetainAllMethodWithHashSet {

	public static void main(String[] args) {

		// creating HashSet object of type String
		HashSet<String> originalSet = new HashSet<String>();

		// adding elements to HashSet object - 4
		originalSet.add("Sundar Pichai");
		originalSet.add("Satya Nadella");  
		originalSet.add("Shiv Nadar");  
		originalSet.add("Shantanu Narayen");

		// Iterating using enhanced for-loop
		System.out.println("Iterating original set\n");
		for(String founder : originalSet) {
			System.out.println(founder);
		}

		// creating HashSet object of type String
		HashSet<String> retainableSet = new HashSet<String>();

		// adding elements to HashSet object - 3
		retainableSet.add("Narayan Murthy");
		retainableSet.add("Sundar Pichai");
		retainableSet.add("Shantanu Narayen");

		originalSet.retainAll(retainableSet);

		// Iterating using enhanced for-loop
		System.out.println("\n\n\nIterating original set,"
				+ " after retainAll() operation\n");
		for(String founder : originalSet) {
			System.out.println(founder);
		}

		// Iterating using enhanced for-loop
		System.out.println("\n\n\nIterating retainable set\n");
		for(String founder : retainableSet) {
			System.out.println(founder);
		}
	}
}

Output:

Iterating original set

Shiv Nadar
Sundar Pichai
Satya Nadella
Shantanu Narayen



Iterating original set, after retainAll() operation

Sundar Pichai
Shantanu Narayen



Iterating retainable set

Sundar Pichai
Shantanu Narayen
Narayan Murthy

 

References:

 

Happy Coding !!
Happy Learning !!

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