meaning of invoking default constructor

Question

I have a homework already done, my teacher get back to me said I need to invoking the default constructor, I am not quite understand what is the difference, can anyone help to explain it to me? Thanks

here is my original code

public Triangle()
    {
        this.side1 = 1.0;
        this.side2 = 1.0;
        this.side3 = 1.0;
    }

and the code that my teacher want me to change

public Triangle()
    {
        this(1.0,1.0,1.0);
    }

Answer 1

Assuming that you already have a constructor like this:

public Triangle(double s1, double s2, double s3) {
    this.side1 = s1;
    this.side1 = s1;
    this.side1 = s1;
}

then your two examples are functionally identical. However it is always good practice to call this constructor instead of repeating yourself with another three assignments.

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As a side note, "invoking the default" constructor is referring to invoking the constructor with no parameters, either through creating an instance or calling this() through another constructor.