Cookbooks
Java
Chapter 3. Numbers
Working with complex numbers

Java:
Working with complex numbers

How to:

Java doesn’t have built-in support for complex numbers, but we can roll our own class or use a library. Here’s a quick example of how to create a simple ComplexNumber class and use it:

public class ComplexNumber {
    private double real;
    private double imaginary;

    public ComplexNumber(double real, double imaginary) {
        this.real = real;
        this.imaginary = imaginary;
    }

    public ComplexNumber add(ComplexNumber other) {
        return new ComplexNumber(this.real + other.real, this.imaginary + other.imaginary);
    }

    // ToString to display complex numbers in a + bi form
    @Override
    public String toString() {
        return String.format("%.1f + %.1fi", real, imaginary);
    }

    // Quick test
    public static void main(String[] args) {
        ComplexNumber c1 = new ComplexNumber(2, 3);
        ComplexNumber c2 = new ComplexNumber(1, 4);

        System.out.println("Sum: " + c1.add(c2));
    }
}

Sample output for the main method will be:

Sum: 3.0 + 7.0i

Deep Dive

Before high-level languages like Java, programmers worked directly with math libraries in languages like Fortran or C to manage complex operations. The concept harks back to the 16th century, credited to mathematicians like Gerolamo Cardano and Rafael Bombelli.

In Java, java.lang.Math is a go-to for essentials but skips complex numbers, probably because not every programmer uses them. Alternatives? Use libraries. Apache Commons Math provides a Complex class packed with methods for manipulation. Here’s why rolling your own is neat though: Lightweight, tailored to your exact needs, and no library overhead.

One important detail: watch out for floating-point precision. Computers can’t represent some numbers exactly, leading to rounding errors. When performing repetitive complex operations, these errors can accumulate!

See Also

For deeper dives and more complex operations, check:

Rounding numbers