Stack removeAll() method in Java with Example

Last Updated : 24 Dec, 2018
The Java.util.Stack.removeAll(Collection col) method is used to remove all the elements from the Stack, present in the collection specified. Syntax: 
Stack.removeAll(Collection col)
Parameters: This method accepts a mandatory parameter col which is the collection whose elements are to be removed from the Stack. Return Value: This method returns true if the Stack is altered due to the operation at all, else False. Exception: The method throws NullPointerException if the specified collection is null. Below programs illustrate the Java.util.Stack.removeAll(Collection col) method: Program 1: Java 
// Java code to illustrate removeAll()
import java.util.*;

public class StackDemo {
    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");

        // Output the Stack
        System.out.println("Stack: " + stack);

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

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

        // Remove the head using remove()
        boolean changed = stack.removeAll(colstack);

        // Print the result
        if (changed)
            System.out.println("Collection removed");
        else
            System.out.println("Collection not removed");

        // Print the final Stack
        System.out.println("Final Stack: " + stack);
    }
}
Output: 
Stack: [Geeks, for, Geeks, 10, 20]
Collection removed
Final Stack: [10, 20]
Program 2: Java 
// Java code to illustrate removeAll()
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(1);
        stack.add(2);
        stack.add(3);
        stack.add(10);
        stack.add(20);

        // Output the Stack
        System.out.println("Stack: " + stack);

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

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

        // Remove the head using remove()
        boolean changed = stack.removeAll(colstack);

        // Print the result
        if (changed)
            System.out.println("Collection removed");
        else
            System.out.println("Collection not removed");

        // Print the final Stack
        System.out.println("Final Stack: " + stack);
    }
}
Output: 
Stack: [1, 2, 3, 10, 20]
Collection not removed
Final Stack: [1, 2, 3, 10, 20]
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