Java EnumSet complementOf() Method

Description

The java.util.EnumSet.complementOf(EnumSet<E> s) method creates an enum set with the same element type as the specified enum set.It contains all the elements of this type that are not contained in the specified set.

Declaration

Following is the declaration for java.util.EnumSet.complementOf() method

public static <E extends Enum<E>> EnumSet<E> complementOf(EnumSet<E> s)

Parameters

s − the enum set from whose complement to initialize this enum set.

Return Value

This method does not return any value.

Exception

NullPointerException − if s is null

Getting Complement Set of EnumSet Example

The following example shows the usage of Java EnumSet complementOf(EnumSet) method to populate the EnumSet instance. We've created a enum Numbers. Then a EnumSet instance is created using a enum value. Using complementOf(EnumSet) method, enumSet is populated with remaining values of enum and resulted enumSet is printed.

package com.tutorialspoint;

import java.util.EnumSet;

public class EnumSetDemo {

   // create an enum
   public enum Numbers {
      ONE, TWO, THREE, FOUR, FIVE
   };

   public static void main(String[] args) {

      // create an EnumSet that has only Numbers.FOUR as element 
      EnumSet<Numbers> set1 = EnumSet.of(Numbers.FOUR);

      // print the set
      System.out.println("Set1:" + set1);

      // create a set2 which has all elements that set1 doesn't have
      EnumSet<Numbers> set2 = EnumSet.complementOf(set1);

      // print the updated set
      System.out.println("Set2:" + set2);

   }
}

Output

Let us compile and run the above program, this will produce the following result −

Set1:[FOUR]
Set2:[ONE, TWO, THREE, FIVE]

Getting Complement Set of EnumSet of Enum with Values Example

The following example shows the usage of Java EnumSet complementOf(EnumSet) method to populate the EnumSet instance. We've created a enum Number. Then a EnumSet instance is created using a enum value. Using complementOf(EnumSet) method, enumSet is populated with remaining values of enum and resulted enumSet is printed.

package com.tutorialspoint;

import java.util.EnumSet;

public class EnumSetDemo {

   // create an enum
   public enum Number {
      ONE("1"), TWO("2"), THREE("3"), FOUR("4"), FIVE("5");

      // instance variable for enum
      private String value;

      public String getValue() {
         return this.value;
      }

      // constructor should be private or protected
      private Number(String value) {
         this.value = value;
      }

      @Override
      public String toString() {
        return this.name() +"(" + this.value + ")";
      }
   };

   public static void main(String[] args) {

      // create an EnumSet that has only Numbers.FOUR as element 
      EnumSet<Number> set1 = EnumSet.of(Number.FOUR);

      // print the set
      System.out.println("Set1:" + set1);

      // create a set2 which has all elements that set1 doesn't have
      EnumSet<Number> set2 = EnumSet.complementOf(set1);

      // print the updated set
      System.out.println("Set2:" + set2);

   }
}

Output

Let us compile and run the above program, this will produce the following result −

Set1:[FOUR(4)]
Set2:[ONE(1), TWO(2), THREE(3), FIVE(5)]