Java HashSet addall() Method

Syntax :

boolean addAll(Collection C)

Parameters: Given parameter C is a collection of any type in java that is to be added to the HashSet.

Return Value: Its returns true if it successfully added the elements of the collection C to this HashSet otherwise it returns False.

Example 1 :  Java Hashset addall() Method Append TreeSet

In this example , Hashset.addAll() method added element of TreeSet to HashSet . We will create HashSet and TreeSet . Then we append element of TreeSet to HashSet Using addAll() method of HashSet.

import java.util.HashSet;
import java.util.TreeSet;

public class Hashsetaddall {
	
	public static void main(String[] args) {
				
		HashSet<String> hashSet = new HashSet<String>();
		hashSet.add("Java");
		hashSet.add("Vogue");
		hashSet.add("Welcomes");

		// print hashset
		System.out.println("hashSet elements : " + hashSet);

		TreeSet<String> treeSet = new TreeSet<String>();

		treeSet.add("You");
		treeSet.add("Thanks");
		
		// print treeSet
		System.out.println("treeSet elements : " + treeSet);
		
		/*
		* Adds all of the elements in the specified
		*  collection to hashset collection
		*/

		hashSet.addAll(treeSet);

		System.out.println("After addAll() hashSet elements : "+hashSet);
	}

}

Output:

hashSet elements : [Java, Vogue, Welcomes]
treeSet elements : [Thanks, You]
After addAll() hashSet elements : [Java, Vogue, Thanks, You, Welcomes]

Example 2 :  Java Hashset addall() Method Append ArrayList

Now we add element of ArrayList to HashSet . We create HashSet and ArrayList of String . We will append element of  ArrayList to HashSet using HashSet addAll method.

import java.util.ArrayList;
import java.util.HashSet;
import java.util.TreeSet;

public class Hashsetaddall1 {

	public static void main(String[] args) {
		
		HashSet<String> hashSet = new HashSet<String>();
		hashSet.add("Java");
		hashSet.add("Vogue");
		hashSet.add("Welcomes");

		// print hashset
		System.out.println("hashSet elements : " + hashSet);

		ArrayList<String> arrayList = new ArrayList<String>();

		arrayList.add("You");
		arrayList.add("Thanks");
		
		// print treeSet
		System.out.println("arrayList elements : " + arrayList);
		
		/*
		* Adds all of the elements in the specified
		*  collection to hashset collection
		*/

		hashSet.addAll(arrayList);

		System.out.println("After addAll() hashSet elements : "+hashSet);
		
	}
}

Output:

hashSet elements : [Java, Vogue, Welcomes]
arrayList elements : [You, Thanks]
After addAll() hashSet elements : [Java, Vogue, Thanks, You, Welcomes]

In this tutorial we have learned java Hashset addall () method . We have added element of collection to HashSet using addAll() . you can lean more java HashSet example for practice .

• A Guide To Hashset
• A Guide To Collection in Java
•  Java Doc -HashSet