Instance of custom object being replaced when another is created java

I have code like,

public class ComplexSO {
    public static double real;
    public static double imaginary;

    public ComplexSO(double cReal, double cImaginary) {
        real = cReal;
        imaginary = cImaginary;
    }

    public static ComplexSO selfSquare() {
        return new ComplexSO(Math.pow(real, 2) - Math.pow(imaginary, 2), 
            2 * real * imaginary);
    }

    public static ComplexSO add(Complex other) {
        return new ComplexSO(real + other.real, imaginary + other.imaginary);
    }

    public static void main(String[] args) {
        ComplexSO c = new ComplexSO(1, 2);
        System.out.println("c.real = " + c.real + ", c.imaginary = " + c.imaginary);
        ComplexSO d = new ComplexSO(2, 3);
        System.out.println("c.real = " + c.real + ", c.imaginary = " + c.imaginary);
    }
}

and when I run this I get the output:

c.real = 1.0, c.imaginary = 2.0

c.real = 2.0, c.imaginary = 3.0

I am not new to object oriented languages (C++ and python), but I am new to java, and this simply makes no sense to me. Please halp.

In Java, static properties of a class are global. There is only one value per class definition. Similarly, static methods operate globally and not on class instances. Simply remove static from real, imaginary, selfSquare, and add and you should see the correct behavior. Your main method will need to remain static.

Because each instance of a class references the same copy of a static variable

So the line ComplexSO d = new ComplexSO(2, 3); references to the static variables double and imaginary and therefore overwrites the previous values 1 and 2