Java – retainAll() method explanation with HashSet

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);
		}
	}
}

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