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));     } } |
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));     } } |
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)