Java Collection removeAll() Method with Examples

The removeAll() method of Java Collection removes those elements from the collection that are contained in the collection which is given as an argument to function.

Syntax

boolean removeAll(Collection<?> c);

Parameters:

• c is the collection containing elements that are removed from the calling collection.

Return Type:

It returns a boolean value. It returns true if the calling collection was modified by the removeAll() method else it returns false.

Example of Collection removeAll() method

Below is the implementation of the above method:

Java

// Java Program to demonstrate
// Collection removeAll() method
import java.io.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

// Driver Class
class Main {
    // main function
    public static void main(String[] args)
    {
        Collection<Integer> list1 = new ArrayList<>();
        list1.add(1);
        list1.add(2);
        list1.add(3);
        list1.add(4);

        System.out.println("Original List: " + list1);

        // ArrayList
        Collection<Integer> list2 = new ArrayList<>();
        list2.add(2);
        list2.add(4);

        System.out.println(
            "List containing elements to be removed from the calling collection(list1): "
            + list2);

        boolean isRemoved = list1.removeAll(list2);

        System.out.println("Elements removed from List1: "
                           + isRemoved);
        System.out.println("Modified list1 after deletion: "
                           + list1);
    }
}

Output

Original List: [1, 2, 3, 4]
List containing elements to be removed from the calling collection(list1): [2, 4]
Elements removed from List1: true
Modified list1 after deletion: [1, 3]

Example 2:

Another example where the collection passed as an argument doesn’t contain any element which could be deleted in original collection.

Java

import java.io.*;
import java.util.ArrayList;
import java.util.List;

// Driver Class
class GFG {
      // main function
    public static void main(String[] args)
    {

        // Initiating list1
        List<Integer> list1 = new ArrayList<Integer>();
        list1.add(1);
        list1.add(2);
        list1.add(3);
        list1.add(4);

        System.out.println("Original List: " + list1);

          // Initiating list2
        List<Integer> list2 = new ArrayList<Integer>();
        list2.add(7);
        list2.add(8);

        System.out.println(
            "List containing elements to be removed from the calling collection(list1): "
            + list2);

          // Using removeAll() method
        boolean isRemoved = list1.removeAll(list2);

        System.out.println("Elements removed from List1: "
                           + isRemoved);
        System.out.println("Modified list1 after deletion: "
                           + list1);
    }
}

Output

Original List: [1, 2, 3, 4]
List containing elements to be removed from the calling collection(list1): [7, 8]
Elements removed from List1: false
Modified list1 after deletion: [1, 2, 3, 4]