CODEWITHSUNDEEP
java2dphysics
user3630439
user3630439

Reputation: 71

polygon Class Java

So I am looking at this 2-D physics impulse engine and I really like to know what is going on in each part of the code. There is one part that I am not understanding at all in the polygon class that defines a polygon.

Here is the link to the code: https://github.com/ClickerMonkey/ImpulseEngine/tree/master/src/org/magnos/impulse

click on the polygon class and scroll down to the method named public Shape clone(). In this method there is "p.u.set( u );". I am not understanding what the meaning of this is at all or what it even does. I would be grateful for anyone that could explain what this single line in the code is doing.

thanks for reading

Upvotes: 0

Views: 338

Answers (1)

MadProgrammer
MadProgrammer

Reputation: 347314

Start by understanding that Polygon extends Shape...

public class Polygon extends Shape

In Shape, it defines u as public final Mat2 u = new Mat2();.

So, in Polygon#clone, it first creates a new instance of a Polygon and the sets this new instance's u object with the current instance of u...

Polygon p = new Polygon();
p.u.set( u ); // or p.u.set( this.u ); if it's easier to understand...

Now, in Mat2, the set(Mat2) method simply copies the properties of the parameter to those of it's own values...

public void set( Mat2 m )
{
    m00 = m.m00;
    m01 = m.m01;
    m10 = m.m10;
    m11 = m.m11;
}

So, basically, what this is doing is copying the properties of the parent Polygon.u (Mat2) to the child/cloned version...

Upvotes: 2

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