To use the IntBinaryOperator functional interface in Java, we should understand that it is part of the java.util.function package and is specifically designed for operations that take two int values as arguments and return an int result. It is typically used for mathematical or logical operations involving two integers.

Here is a detailed guide on using IntBinaryOperator:

1. Functional Interface Definition

@FunctionalInterface
public interface IntBinaryOperator {
    int applyAsInt(int left, int right);
}

• Method: applyAsInt(int left, int right).
  • Takes two int arguments (left and right).
  • Returns an int.

2. Using a Lambda Expression

We can implement IntBinaryOperator using a lambda expression to define operations like addition, subtraction, multiplication, etc.

Example:

package org.kodejava.util.function;

import java.util.function.IntBinaryOperator;

public class IntBinaryOperatorExample {
  public static void main(String[] args) {
    // Define a lambda to add two integers
    IntBinaryOperator addition = (a, b) -> a + b;

    // Use the operator
    int result = addition.applyAsInt(5, 3);
    System.out.println("5 + 3 = " + result);

    // Define another operator to find the maximum of two integers
    IntBinaryOperator maxOperator = Math::max;

    // Use the operator
    int max = maxOperator.applyAsInt(10, 20);
    System.out.println("Max of 10 and 20 is: " + max);
  }
}

3. Using Method References

We can use predefined methods like Math::max or Math::min as implementations of IntBinaryOperator.

Example:

package org.kodejava.util.function;

import java.util.function.IntBinaryOperator;

public class BinaryMethodReferenceExample {
  public static void main(String[] args) {
    // Use Math::max with IntBinaryOperator
    IntBinaryOperator maxOperator = Math::max;
    System.out.println("Max of 12 and 7 is: " + maxOperator.applyAsInt(12, 7));

    // Use Math::min with IntBinaryOperator
    IntBinaryOperator minOperator = Math::min;
    System.out.println("Min of 12 and 7 is: " + minOperator.applyAsInt(12, 7));
  }
}

4. Combining Multiple IntBinaryOperator Instances

We can combine multiple IntBinaryOperator objects to perform a sequence of operations.

Example:

package org.kodejava.util.function;

import java.util.function.IntBinaryOperator;

public class CombineOperators {
  public static void main(String[] args) {
    // Operator to add two numbers
    IntBinaryOperator add = (a, b) -> a + b;

    // Operator to multiply two numbers
    IntBinaryOperator multiply = (a, b) -> a * b;

    // Combining by applying addition first, then multiplication
    int combinedResult = multiply.applyAsInt(add.applyAsInt(2, 3), 4);

    // Outputs 20
    System.out.println("Result of (2 + 3) * 4 is: " + combinedResult);
  }
}

5. Using IntBinaryOperator in Streams

IntBinaryOperator can be used in stream operations, particularly for reductions or aggregations where binary operations are applied repeatedly, like finding sums or products of integer lists.

Example:

package org.kodejava.util.function;

import java.util.function.IntBinaryOperator;
import java.util.stream.IntStream;

public class StreamReduceExample {
  public static void main(String[] args) {
    IntBinaryOperator sumOperator = (a, b) -> a + b;

    // Using IntBinaryOperator with Stream
    int sum = IntStream.of(1, 2, 3, 4, 5) // Stream of numbers
            .reduce(0, sumOperator);       // Apply sum operation

    System.out.println("Sum of numbers: " + sum);

    // Using a multiplication operator
    IntBinaryOperator productOperator = (a, b) -> a * b;

    int product = IntStream.of(1, 2, 3, 4)
            .reduce(1, productOperator);

    System.out.println("Product of numbers: " + product);
  }
}

Summary

• IntBinaryOperator simplifies binary operations on int values, avoiding boxing overhead associated with BinaryOperator<Integer>.
• Use it for mathematical, logical, or aggregation operations.
• It can be implemented using lambdas or method references.
• Common use cases include streams, reduction operations, or combining multiple operators.