Question

Ok i need some help with a little syntax problem. I have a class and i want it to put it into an arraylist, and populate the arraylist using a for loop.
Here is an example of what i want:

    public class w{
    int x;
    int y;
    }
    Arraylist m = new Arraylist();
    for(int i=0; i<n;i++)
  {
          m[i].add(w.x);
          m[i].add(w.y);

  }

Yes the code isn’t functioning its just an example of what i want it to do. I don’t know the syntax and I want an arraylist with classes that can be retrieved by giving the i and get the both variables only by that ‘i’;
Any help will be apreciated. Thank you very much for your time, sorry for the lousy description but i can’t be more specific.

Answer 1

It’s not clear what you’re trying to accomplish, but perhaps this will be enough of a guide as to how to use ArrayList properly. I changed your class name from w to W to match the usual Java coding conventions.

public class W {
    int x;
    int y;
    public W(int x, int y) {
        this.x = x;
        this.y = y;
    }
}

ArrayList<W> m = new ArrayList<W>(); // can be 'new ArrayList<>()` in Java 7
m.add(new W(1, 2));
m.add(new W(5,-3));
// etc.

for (int i=0; i<m.size(); i++) {
    W w = m.get(i);
    System.out.println("m[" + i + "]=(" + w.x + "," + w.y + ")");
}

for (W w : m) {
    System.out.println("next W: (" + w.x + "," + w.y + ")");
}