Stack addAll(Collection) method in Java with Example

The addAll(Collection) method of Stack Class is used to append all of the elements from the collection passed as a parameter to this function to the end of a Stack keeping in mind the order of return by the collection’s iterator.

Syntax:

boolean addAll(Collection C)

Parameters: The method accepts a mandatory parameter C which is a collection of ArrayList. It is the collection whose elements are needed to be appended at the end of the Stack.

Return Value: The method returns True if at least one action of append is performed, else False.

Below program illustrate the Java.util.Stack.addAll() method:

// Java code to illustrate boolean addAll()
import java.util.*;
import java.util.ArrayList;

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

        // Creating an empty Stack
        Stack<String> stack = new Stack<String>();

        // Use add() method to add elements in the Stack
        stack.add("Geeks");
        stack.add("for");
        stack.add("Geeks");
        stack.add("10");
        stack.add("20");

        // A collection is created
        Collection<String> c = new ArrayList<String>();
        c.add("A");
        c.add("Computer");
        c.add("Portal");
        c.add("for");
        c.add("Geeks");

        // Displaying the Stack
        System.out.println("The Stack is: " + stack);

        // Appending the collection to the Stack
        stack.addAll(c);

        // Clearing the Stack using clear() and displaying
        System.out.println("The new Stack is: " + stack);
    }
}

Output:

The Stack is: [Geeks, for, Geeks, 10, 20]
The new Stack is: [Geeks, for, Geeks, 10, 20, A, Computer, Portal, for, Geeks]

Example 2:

// Java code to illustrate
// boolean add(Object element)

import java.util.*;

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

        // Creating an empty Stack
        Stack<Integer> stack
            = new Stack<Integer>();

        // Use add() method
        // to add elements in the Stack
        stack.add(10);
        stack.add(20);
        stack.add(30);
        stack.add(40);
        stack.add(50);

        // A collection is created
        Collection<Integer> c = new ArrayList<Integer>();
        c.add(1);
        c.add(2);
        c.add(3);

        // Displaying the Stack
        System.out.println("The Stack is: " + stack);

        // Appending the collection to the Stack
        stack.addAll(c);

        // Clearing the Stack using clear() and displaying
        System.out.println("The new Stack is: " + stack);
    }
}

Output:

The Stack is: [10, 20, 30, 40, 50]
The new Stack is: [10, 20, 30, 40, 50, 1, 2, 3]