Run method based on input, without if-statement logic

Question

I have one single method that takes in 2 parameters:

public void generate(int size, String animal){
      // output a picture of the "animal" on java.swing of size "size"
}

So the possibility of the animals are Monkey, Giraffe, Dog, Cat, and Mouse. However, the assignment specifies that I can only have 1 method, no if-statements / cases / ternary operators, no external classes. So in the method, I have to create all 5 of these animals:

public void generate(int size, String animal){
      // output picture of Monkey
      // output picture of Giraffe
      // output picture of Dog
      // output picture of Cat
      // output picture of Mouse
}

So in turn, I was thinking I have to only make part of the method run based on the inputs. Is there any way to do this? The professor's hint was to use "multiple dispatch", but if there is only 1 method, how is this possible?

What does "external class" mean? Class written by someone else? — Robin Green, Nov 30 '13 at 17:45
What about overloading. You could overload the method so it choses the right method for the object you pass in to the method. — Skeletor, Nov 30 '13 at 17:49
I don't know if I understood the question, but I'd do something like `BufferedImage myPicture = ImageIO.read(new File("pictures/" + animal + ".png")); JLabel picLabel = new JLabel(new ImageIcon(myPicture));` — StepTNT, Nov 30 '13 at 17:51
external class as in you can't define any other classes. I looked at overloading but there is only 1 method so I can't overload. — Stevantti, Nov 30 '13 at 18:03
I'm confused, because you accepted my answer, yet this involves external classes - unless you make them inner classes. — Robin Green, Dec 01 '13 at 07:36

score 0 · Accepted Answer · answered Nov 30 '13 at 17:47

0

public interface Animal {
   public void draw(int size);
}

public class Monkey implements Animal {
   public void draw(int size) {
      // ...
   }
}

etc.

answered Nov 30 '13 at 17:47

Robin Green

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score 0 · Answer 2 · answered Nov 30 '13 at 18:05

Since you do not want to use if/else/switch-case , assuming each type of animal is a class you can try this implementation.

public class Test {

static Map<String, Animal> animalTypeMap = new HashMap<String, Animal>();
static {
    animalTypeMap.put("Monkey", new Monkey());
    // put other animals in the map

}

public static void main(String[] args) {

    Test test = new Test();
    test.generate(5, "Monkey");

}

public void generate(int size, String animal) {
    // output picture of Monkey
    Animal animalObj = animalTypeMap.get(animal);
    animalObj.draw(size);
    // output picture of Giraffe
    // output picture of Dog
    // output picture of Cat
    // output picture of Mouse
}

}

interface Animal {
public void draw(int size);
// .....more methods

}

class Monkey implements Animal {

// ...implement methods
@Override
public void draw(int size) {
    System.out.println("Monkey of size " + size + " drawn");

}
// ...more methods
}

// ....more classes implementing animal interface

Run method based on input, without if-statement logic

2 Answers2