What is the BinaryOperator functional interface in Java?

BinaryOperator is a functional interface, which takes in two arguments of the same type and returns a result that is also of the same type. This interface extends the BiFunction interface. This interface has two methods:

  • minBy(Comparator<? super T> comparator)
  • maxBy(Comparator<? super T> comparator)

The BinaryOperator interface is defined in the java.util.function package. To import the BinaryOperator interface, we check the following import statement:

import java.util.function.BinaryOperator;

minBy(Comparator<? super T> comparator)

This method returns a BinaryOperator, which returns the lesser/minimum of the two given inputs, as per the specified Comparator.

Syntax

public static <T> BinaryOperator<T> minBy(Comparator<? super T> comparator)

Parameters

  • Comparator<? super T> comparator: This is the comparator that is used to compare the inputs.

Return value

This method returns a BinaryOperator.

Code

import java.util.Comparator;
import java.util.function.BinaryOperator;
public class Main{
    public static void main(String[] args) {
        // Comparator for the comparison of the input arguments
        Comparator<Integer> integerComparator = Comparator.naturalOrder();
        // BinaryOperator to get the minimum of the input arguments
        BinaryOperator<Integer> integerIntegerBinaryOperator = BinaryOperator.minBy(integerComparator);
        // first argument
        int arg1 = 2;
        // second argument
        int arg2 = 4;
        // Test the arguments
        System.out.printf("minimum(%s, %s) = %s", arg1, arg2, integerIntegerBinaryOperator.apply(arg1, arg2));
    }
}

Code explanation

  • Lines 1-2: We import the relevant packages.
  • Line 9: We define a Comparator for the comparison of the input arguments.
  • Line 12: We define a BinaryOperator to get the minimum of the input arguments.
  • Line 15: We define the first argument.
  • Line 18: We define the second argument.
  • Line 21: We test the minBy() method of the BinaryOperator, using the apply method on the arguments defined in lines 15 and 18.

maxBy(Comparator<? super T> comparator)

This method returns a BinaryOperator, which returns the greater/maximum of the two given inputs, as per the specified Comparator.

Syntax

public static <T> BinaryOperator<T> maxBy(Comparator<? super T> comparator)

Parameters

  • Comparator<? super T> comparator: This is the comparator that is used to compare the inputs.

Return value

This method returns a BinaryOperator.

Code

import java.util.Comparator;
import java.util.function.BinaryOperator;
public class Main{
    public static void main(String[] args) {
        // Comparator for the comparison of the input arguments
        Comparator<Integer> integerComparator = Comparator.naturalOrder();
        // BinaryOperator to get the maximum of the input arguments
        BinaryOperator<Integer> integerIntegerBinaryOperator = BinaryOperator.maxBy(integerComparator);
        // first argument
        int arg1 = 2;
        // second argument
        int arg2 = 4;
        // Test the arguments
        System.out.printf("maximum(%s, %s) = %s", arg1, arg2, integerIntegerBinaryOperator.apply(arg1, arg2));
    }
}

Code explanation

  • Lines 1–2: We import the relevant packages.
  • Line 9: We define a Comparator for the comparison of the input arguments.
  • Line 12: We define a BinaryOperator to get the maximum of the input arguments, using the maxBy() method.
  • Line 15: We define the first argument.
  • Line 18: We define the second argument.
  • Line 21: We test the maxBy() method of the BinaryOperator, using the apply method on the arguments defined in lines 15 and 18.

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