What is the CopyOnWriteArraySet.containsAll method in Java?

Overview

The containsAll() method checks if all the elements of a specific collection object are also present in the CopyOnWriteArraySet object.

Note: CopyOnWriteArraySet is a thread-safe version of setA collection that contains no duplicate elements.. CopyOnWriteArraySet internally uses CopyOnWriteArrayList for its operations. All of the write operations, like add and set, make a fresh copy of the underlying array and operate on the cloned array. Read more about CopyOnWriteArraySet here.

Syntax

public boolean containsAll(Collection<?> c)

Parameters

The containsAll() method takes the collection that we check for in the set as an argument.

Return value

The containsAll() method returns true if all the elements of the passed collection are present in the set. Otherwise, it returns false.

Code

The code below demonstrates how we can use the containsAll() method.

import java.util.concurrent.CopyOnWriteArraySet;
import java.util.ArrayList;
class ContainsAllExample {
    public static void main( String args[] ) {
        // create a CopyOnWriteArraySet object which can contain integer elements 
        CopyOnWriteArraySet<Integer> set = new CopyOnWriteArraySet<>();
        // add three elements to it
        set.add(1);
        set.add(2);
        set.add(3);
        // create a new arraylist 
        ArrayList<Integer> list1 = new ArrayList<>();
        list1.add(1);
        list1.add(3);
        System.out.println("The set is "+ set);
        System.out.println("\nlist1 is "+ list1);
        // use contiansAll method to check if all element of list1 is present in list
        System.out.println("If set contains all elements of list1 : "+ set.containsAll(list1));
        // create a new list 
        ArrayList<Integer> list2 = new ArrayList<>();
        list2.add(4);
        
        System.out.println("\nlist2 is "+ list2);
        // use contiansAll method to check if all element of list2 is present in list
        System.out.println("If set contains all elements of list2 : "+ set.containsAll(list2));
        
    }
}

Code explanation

Lines 1 to 2: We import the CopyOnWriteArraySet and ArrayList classes.
Line 6: We create an object named set for the CopyOnWriteArraySet class.
Lines 8 to 10: We add three elements (1, 2, and 3) to the created set object.
Line 13: We create a new ArrayList object named list1 and add the elements 1 and 3 to it.
Line 20: We call the containsAll() method to check if all the elements of list1 are present in set. In this case, the condition returns true because all the elements (1 and 3) of list1 are also present in set.
Line 2*: We create a new ArrayList object named list2 and add the element 4 to it.
Line 29: We call the containsAll() method to check if all the elements of list2 are present in set. In this case, the condition returns false because element 4 of list2 is not present in set.

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)

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