AbstractCollection addAll() Method in Java with Examples

The addAll(Collection C) method of Java AbstractCollection is used to append all of the elements from a mentioned collection to this collection. The elements are added randomly without following any specific order. 

Syntax:

boolean addAll(Collection C)

Parameters: The parameter C is a collection of any type that is to be added to the collection. 

Return Value: The method returns true if it successfully appends the elements of the collection C to the existing collection otherwise it returns False. 

Below programs illustrate the AbstractCollection.addAll() method: 

Program 1:

Java

// Java code to illustrate addAll()
// method of AbstractCollection

import java.util.*;
import java.util.AbstractCollection;

public class AbstractCollectionDemo {
    public static void main(String args[])
    {

        // Creating an empty collection
        AbstractCollection<String>
            abs1 = new TreeSet<String>();

        // Use add() method to add
        // elements into the Collection
        abs1.add("Welcome");
        abs1.add("To");
        abs1.add("Geeks");
        abs1.add("4");
        abs1.add("Geeks");
        abs1.add("TreeSet");

        // Displaying the Collection
        System.out.println("AbstractCollection 1: "
                           + abs1);

        // Creating another Collection
        AbstractCollection<String>
            abs2 = new TreeSet<String>();

        // Displaying the Collection
        System.out.println("AbstractCollection 2: "
                           + abs2);

        // Using addAll() method to Append
        abs2.addAll(abs1);

        // Displaying the Collection
        System.out.println("AbstractCollection 2: "
                           + abs2);
    }
}

Output:

AbstractCollection 1: [4, Geeks, To, TreeSet, Welcome]
AbstractCollection 2: []
AbstractCollection 2: [4, Geeks, To, TreeSet, Welcome]

Program 2:

Java

// Java code to illustrate addAll()
// method of AbstractCollection

import java.util.*;
import java.util.AbstractCollection;

public class AbstractCollectionDemo {
    public static void main(String args[])
    {

        // Creating an empty collection
        AbstractCollection<Integer>
            abs1 = new TreeSet<Integer>();

        // Use add() method to add
        // elements into the Collection
        abs1.add(10);
        abs1.add(20);
        abs1.add(30);
        abs1.add(40);
        abs1.add(50);

        // Displaying the Collection
        System.out.println("AbstractCollection 1: "
                           + abs1);

        // Creating another Collection
        AbstractCollection<Integer>
            abs2 = new TreeSet<Integer>();

        // Displaying the Collection
        System.out.println("AbstractCollection 2: "
                           + abs2);

        // Using addAll() method to Append
        abs2.addAll(abs1);

        // Displaying the Collection
        System.out.println("AbstractCollection 2: "
                           + abs2);
    }
}

Output:

AbstractCollection 1: [10, 20, 30, 40, 50]
AbstractCollection 2: []
AbstractCollection 2: [10, 20, 30, 40, 50]