Java IntStream mapToDouble() Method

The mapToDouble() method in Java, part of the java.util.stream.IntStream interface, is used to apply a given function to each element of the stream, producing a new DoubleStream of the results. This method is useful when you need to transform the elements of an IntStream into double values.

Table of Contents

1. Introduction
2. mapToDouble() Method Syntax
3. Understanding mapToDouble()
4. Examples
   • Basic Usage
   • Using mapToDouble() with Other Stream Operations
5. Real-World Use Case
6. Conclusion

Introduction

The mapToDouble() method returns a DoubleStream consisting of the results of applying a given function to the elements of the original IntStream. This method is an intermediate operation, meaning it returns a new stream and does not modify the original stream.

mapToDouble() Method Syntax

The syntax for the mapToDouble() method is as follows:

DoubleStream mapToDouble(IntToDoubleFunction mapper)

Parameters:

• mapper: An IntToDoubleFunction that represents the function to be applied to each element of the stream.

Returns:

• A new DoubleStream consisting of the results of applying the given function to the elements of the original stream.

Throws:

• This method does not throw any exceptions.

Understanding mapToDouble()

The mapToDouble() method processes each element of the stream and applies the specified function to it, resulting in a new stream containing double values. This is useful for performing operations that require floating-point arithmetic or conversions.

Examples

Basic Usage

To demonstrate the basic usage of mapToDouble(), we will create an IntStream and use mapToDouble() to convert each integer to its corresponding double value.

Example

import java.util.stream.DoubleStream;
import java.util.stream.IntStream;

public class MapToDoubleExample {
    public static void main(String[] args) {
        IntStream intStream = IntStream.of(1, 2, 3, 4, 5);

        // Use mapToDouble() to convert each integer to a double value
        DoubleStream doubleStream = intStream.mapToDouble(n -> (double) n);

        // Print the double values
        doubleStream.forEach(System.out::println);
    }
}

Output:

1.0
2.0
3.0
4.0
5.0

Using mapToDouble() with Other Stream Operations

This example shows how to use mapToDouble() in combination with other stream operations, such as filtering.

Example

import java.util.stream.DoubleStream;
import java.util.stream.IntStream;

public class MapToDoubleWithOtherOperationsExample {
    public static void main(String[] args) {
        IntStream intStream = IntStream.range(1, 10);

        // Filter even numbers and map them to their square roots
        DoubleStream processedStream = intStream.filter(n -> n % 2 == 0)
                                                .mapToDouble(Math::sqrt);

        // Print the processed elements
        processedStream.forEach(System.out::println);
    }
}

Output:

1.4142135623730951
2.0
2.449489742783178
2.8284271247461903

Real-World Use Case

Converting Prices to Discounts

In real-world applications, the mapToDouble() method can be used to convert prices (integer values) to discounts (double values) based on a predefined discount rate.

Example

import java.util.stream.DoubleStream;
import java.util.stream.IntStream;

public class ConvertPricesExample {
    public static void main(String[] args) {
        IntStream prices = IntStream.of(100, 200, 300, 400, 500);
        double discountRate = 0.1;

        // Convert prices to discounts
        DoubleStream discounts = prices.mapToDouble(price -> price * discountRate);

        // Print the discounts
        discounts.forEach(discount -> System.out.println("Discount: " + discount));
    }
}

Output:

Discount: 10.0
Discount: 20.0
Discount: 30.0
Discount: 40.0
Discount: 50.0

Conclusion

The IntStream.mapToDouble() method is used to apply a given function to each element of the stream, producing a new DoubleStream of the results. This method is particularly useful for transforming the elements of an IntStream into double values. By understanding and using this method, you can efficiently manage and process streams of integer values in your Java applications, performing necessary transformations to double values when needed.