I have a buch of classes written by me I would like to reuse in my future projects. It will be great to do this just improting a custom library.
How should I do that? What should I know and from where should I start?
I read this page  https://code.google.com/p/processing/wiki/LibraryBasics but it looks a bit tricky to me? It seems I have to write it in java and compile some files... I'm not sure this is what I need. I just want to reuse some classes without copy/paste them every time :-/

I'm planning to write a basic synthesizer and I'd love to write it in Processing but I'm not sure it is possible. Do Processing provides a low level sound API or is there a library for this? If so where can I find documentation about it?

I have a class with a lot of attributes. Each of those attributes have a default value.

1. class MyClass{
2.       int a1=1;
3.       int a2=2;
4.       int a3=3;
5.       ...
6.       MyClass(){
7.             //in this constructor no parameters are passed so every attribute keeps it's default value
8.       }
9. }

Now I want to instantiate an object of this class by passing to the constructor only the parameters I want to be different from the default value.

1. MyClass mc = new MyClass(a1=100, a5=500);
   // I would like a constructor like this where I set the value to only some attributes of the class while others keep their default value

How should I do this? I hope I don't have to write a constructor for every combination of parameters :-/

As the title says, I would like to resize the display window during the execution.

In my program, every time I click on the window I can choose an image to display and I would like the display size fits every time the size of the image displayed.
Something like this:

2. PImage img;
3. 
   
4. void setup(){
5.   pickImage();
6. }
7. 
   
8. void draw(){
9. }
10. 
    
11. void mousePressed(){
12.     pickImage();
13. }
14. 
    
15. void pickImage(){
16.   String path=selectInput();
17.   img=loadImage(path);
18.   size(img.width,img.height);
19.   image(img,0,0,width,height);
20. }

But the display window size change only the first time! Any suggestions?

Say I have this code: