Set containsAll() method in Java with Examples

The containsAll() method of Java Set is used to check whether two sets contain the same elements or not. It takes one set as a parameter and returns True if all of the elements of this set is present in the other set.

Syntax:

public boolean containsAll(Collection C)

Parameters: The parameter C is a Collection. This parameter refers to the set whose elements occurrence is needed to be checked in this set.

Return Value: The method returns True if this set contains all the elements of other set otherwise it returns False.

Below programs illustrate the Set.containsAll() method:

Program 1:

// Java code to illustrate
// Set containsAll()

import java.util.*;

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

        // Creating an empty set
        Set<String>
            set = new HashSet<String>();

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

        // prints the set
        System.out.println("Set 1: "
                           + set);

        // Creating another empty set
        Set<String>
            set2 = new HashSet<String>();

        // Use add() method to
        // add elements in the set
        set2.add("Geeks");
        set2.add("for");
        set2.add("Geeks");
        set2.add("10");
        set2.add("20");

        // prints the set
        System.out.println("Set 2: "
                           + set2);

        // Check if the set
        // contains same elements
        System.out.println("\nDoes set 1 contains set 2?: "
                           + set.containsAll(set2));
    }
}

Output:

Set 1: [Geeks, for, 20, 10]
Set 2: [Geeks, for, 20, 10]

Does set 1 contains set 2?: true

Program 2:

// Java code to illustrate boolean containsAll()

import java.util.*;

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

        // Creating an empty set
        Set<String>
            set = new HashSet<String>();

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

        // prints the set
        System.out.println("Set 1: "
                           + set);

        // Creating another empty set
        Set<String>
            set2 = new HashSet<String>();

        // Use add() method to
        // add elements in the set
        set2.add("10");
        set2.add("20");

        // prints the set
        System.out.println("Set 2: "
                           + set2);

        // Check if the set
        // contains same elements
        System.out.println("\nDoes set 1 contains set 2: "
                           + set.containsAll(set2));
    }
}

Output:

Set 1: [Geeks, for]
Set 2: [20, 10]

Does set 1 contains set 2: false

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Set.html#containsAll(java.util.Collection)