Introduction

In Java, the `ToDoubleBiFunction` interface is a functional interface that represents a function that accepts two arguments and produces a `double` result. It is part of the `java.util.function` package and is commonly used for operations that involve two input values and return a `double`.

1. What is `ToDoubleBiFunction`?
2. Methods and Syntax
3. Examples of `ToDoubleBiFunction`
4. Real-World Use Case
5. Conclusion

1. What is ToDoubleBiFunction?

`ToDoubleBiFunction` is a functional interface that takes two arguments of types `T` and `U` and returns a `double` result. It is useful for scenarios where two values need to be processed or combined to produce a `double`.

2. Methods and Syntax

The main method in the `ToDoubleBiFunction` interface is:

• `double applyAsDouble(T t, U u)`: Applies this function to the given arguments and returns a `double` result.

Syntax

``````ToDoubleBiFunction<T, U> function = (T t, U u) -> {
// operation on t and u
return result;
};
``````

3. Examples of ToDoubleBiFunction

Example 1: Calculating Average of Two Numbers

``````import java.util.function.ToDoubleBiFunction;

public class AverageCalculator {
public static void main(String[] args) {
// Define a ToDoubleBiFunction that calculates the average of two integers
ToDoubleBiFunction<Integer, Integer> average = (a, b) -> (a + b) / 2.0;

double result = average.applyAsDouble(10, 20);
System.out.println("Average: " + result);
}
}
``````

Output:

``````Average: 15.0
``````

Example 2: Calculating Distance Between Two Points

``````import java.util.function.ToDoubleBiFunction;

public class DistanceCalculator {
public static void main(String[] args) {
// Define a ToDoubleBiFunction that calculates the Euclidean distance between two points
ToDoubleBiFunction<int[], int[]> distance = (p1, p2) -> Math.sqrt(Math.pow(p2[0] - p1[0], 2) + Math.pow(p2[1] - p1[1], 2));

double result = distance.applyAsDouble(new int[]{1, 2}, new int[]{4, 6});
System.out.println("Distance: " + result);
}
}
``````

Output:

``````Distance: 5.0
``````

4. Real-World Use Case: Calculating Weighted Score

In applications, `ToDoubleBiFunction` can be used to calculate a weighted score from two values.

``````import java.util.function.ToDoubleBiFunction;

public class WeightedScoreCalculator {
public static void main(String[] args) {
// Define a ToDoubleBiFunction to calculate a weighted score
ToDoubleBiFunction<Integer, Double> weightedScore = (score, weight) -> score * weight;

double result = weightedScore.applyAsDouble(85, 0.75);
System.out.println("Weighted Score: " + result);
}
}
``````

Output:

``````Weighted Score: 63.75
``````

Conclusion

The `ToDoubleBiFunction` interface is used in Java for operations involving two inputs that produce a `double` result. It is particularly beneficial in scenarios requiring mathematical calculations or data processing. Using `ToDoubleBiFunction` can lead to cleaner and more efficient code, especially in functional programming contexts.