Java DoubleToLongFunction

Introduction

In Java, the DoubleToLongFunction interface is a functional interface that represents a function that accepts a double-valued argument and produces a long result. It is part of the java.util.function package and is commonly used for operations that convert or process double values into long values.

Table of Contents

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

1. What is DoubleToLongFunction?

DoubleToLongFunction is a functional interface that takes a double as input and returns a long. It is useful for scenarios where double values need to be converted to long values, such as rounding or type conversion.

2. Methods and Syntax

The main method in the DoubleToLongFunction interface is:

• long applyAsLong(double value): Applies this function to the given argument and returns a long result.

Syntax

DoubleToLongFunction doubleToLongFunction = (double value) -> {
    // operation on value
    return result;
};

3. Examples of DoubleToLongFunction

Example 1: Rounding a Double to a Long

import java.util.function.DoubleToLongFunction;

public class RoundingExample {
    public static void main(String[] args) {
        // Define a DoubleToLongFunction that rounds a double to a long
        DoubleToLongFunction roundToLong = (value) -> Math.round(value);

        long result = roundToLong.applyAsLong(5.7);

        System.out.println("Rounded Value: " + result);
    }
}

Output:

Rounded Value: 6

Example 2: Converting Double to Long by Truncation

import java.util.function.DoubleToLongFunction;

public class TruncateExample {
    public static void main(String[] args) {
        // Define a DoubleToLongFunction that truncates a double to a long
        DoubleToLongFunction truncateToLong = (value) -> (long) value;

        long result = truncateToLong.applyAsLong(9.8);

        System.out.println("Truncated Value: " + result);
    }
}

Output:

Truncated Value: 9

4. Real-World Use Case: Converting Currency to Cents

In financial applications, DoubleToLongFunction can be used to convert an amount in dollars to cents.

import java.util.function.DoubleToLongFunction;

public class CurrencyConverter {
    public static void main(String[] args) {
        // Define a DoubleToLongFunction to convert dollars to cents
        DoubleToLongFunction dollarsToCents = (amount) -> (long) (amount * 100);

        long cents = dollarsToCents.applyAsLong(10.75);

        System.out.println("Cents: " + cents);
    }
}

Output:

Cents: 1075

Conclusion

The DoubleToLongFunction interface is used in Java for converting double values to long results. It is particularly beneficial in applications requiring type conversion or mathematical processing. Using DoubleToLongFunction can lead to cleaner and more efficient code, especially in functional programming contexts.