The containsAll() method of Java HashSet 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 HashSet.containsAll() method:
Program 1:
// Java code to illustrate// HashSet containsAll()  import java.util.*;  class HashSetDemo {    public static void main(String args[])    {          // Creating an empty set        HashSet<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("HashSet 1: "                           + set);          // Creating another empty set        HashSet<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("HashSet 2: "                           + set2);          // Check if the set        // contains same elements        System.out.println("\nDoes set 1 contains set 2: "                           + set.containsAll(set2));    }} |
Output:
HashSet 1: [Geeks, for, 20, 10] HashSet 2: [Geeks, for, 20, 10] Does set 1 contains set 2: true
Program 2:
// Java code to illustrate boolean containsAll()  import java.util.*;  class HashSetDemo {    public static void main(String args[])    {          // Creating an empty set        HashSet<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("HashSet 1: "                           + set);          // Creating another empty set        HashSet<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("HashSet 2: "                           + set2);          // Check if the set        // contains same elements        System.out.println("\nDoes set 1 contains set 2: "                           + set.containsAll(set2));    }} |
Output:
HashSet 1: [Geeks, for] HashSet 2: [20, 10] Does set 1 contains set 2: false
