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Reputation: 7190

Java, how to create a class similar to Math

I am trying to write a porting of glm in java.

At the moment I created a package jglm and inside this package there are all the different classes Mat4, Vec4, Vec3, etc..

Such as:

public class Mat {

    protected float[] matrix;
    protected int order;
}

I can call them by typing 

jgml.Mat4 modelviewMatrix = new Jgml.Mat4(1.0f);

And this is fine..

Now I am writing also some methods, like 

mix(x, y, lerp)

And I also would like to use this as stated, that is 

float value = jglm.mix(x, y, lerp)

But of course in this case Jglm must be a class...

Is there a way to conjugate the two things together?

Edit: If I create a class jglm.Jglm

package jglm;

/**
 *
 * @author gbarbieri
 */
public class Jglm {

    public class Mat {

        protected float[] matrix;
        protected int order;
    }

    public class Mat4 extends Mat {

        public Vec4 c0;
        public Vec4 c1;
        public Vec4 c2;
        public Vec4 c3;

        public Mat4(float value) {

            order = 4;

            matrix = new float[16];

            for (int i = 0; i < 4; i++) {
                matrix[i * 5] = value;
            }
            c0 = new Vec4(matrix, 0);
            c1 = new Vec4(matrix, 4);
            c2 = new Vec4(matrix, 8);
            c3 = new Vec4(matrix, 12);
        }

        public float[] toFloatArray() {
            return new float[]{
                c0.x, c0.y, c0.z, c0.w,
                c1.x, c1.y, c1.z, c1.w,
                c2.x, c2.y, c2.z, c2.w,
                c3.x, c3.y, c3.z, c3.w,};
        }
    }

    public static float mix(float start, float end, float lerp) {
        return (start + lerp * (end - start));
    }
}

When I try to instantiate 

cameraToClipMatrix_mat4 = new Jglm.Mat4(1.0f);

I get "an enclosing instance that contains Jglm.Mat4 is required"

Upvotes: 0

Views: 1567

Answers (3)

Marko Topolnik
Marko Topolnik

Reputation: 200306

At the moment I created a package Jglm and inside this package there are all the different classes Mat4, Vec4, Vec3, etc..

In Java, packages must be named in all lowercase. Naming it the way you did will surprise anyone who looks at your code and may also cause serious name-resolution issues for the compiler.

It is also customary to import all classes we are using so we refer to them just by their simple name in code. Perhaps you could consider declaring

package org.example.jglm;

public class Jglm {
  public static void mix(double x, double y, Lerp lerp) {
    ...
  }
}

on the client side, you'd write

import org.example.Jglm;

void someMethod() {
  Jglm.mix(x,y,lerp);
}

In general, when you need some pure functions in your code, then declare them as static methods. Look at java.lang.Math source code for guidance.

Upvotes: 2

Juned Ahsan
Juned Ahsan

Reputation: 68725

Having all the methods in your Jglm class as static will enable the method calls, both by instance and by classname.

Upvotes: 1

Suresh Atta
Suresh Atta

Reputation: 122026

Declare all your methods in Mat class as static

which have the static modifier in their declarations, should be invoked with the class name, without the need for creating an instance of the class.

Ex: ClassName.methodName(args)

See Class Methods in http://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html

Upvotes: 2

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