Initialize a Class, if it it has in its constructor an Interface as a Parameter?

Question

There is a Class called TrianglePictureFilter, which has a the following constructor:

public TrianglePictureFilter(IPointGenerator pointGenerator) {
        super(pointGenerator);
    }

IPointGenerator is an interface:

import java.awt.Point;

/**
 * Point generator interface, providing points for generating geometric primitives.
 */
public interface IPointGenerator {
    /**
     * Generates the next (random) point.
     * 
     * @return a new point
     */
    public Point nextPoint();
}

I would like to use one of the methods of TrianglePictureFilter in another class, I have imported it, but I do not know how to initialize it, or to be more precise how to initialize the parameter in the constructor. Can somebody help me with that?

Answer 1

So, if you have not already implemented your IPointGenerator class, you would do it like this:

public class TrianglePictureFilter implements IPointGenerator {

    public Point nextPoint() {
        // Return your random point.
    }

}

I'm not sure if this exactly what you were asking for, but to use this code, it would be as simple as this:

TrianglePictureFilter filter = new TrianglePictureFilter();
Point randomPoint = filter.nextPoint();

Is this the kind of behavior you were looking for? If not, you probably don't want to use an interface .

Answer 2

An object must inherit the IPointGenerator interface like so:

class AClass: IPointerGenerator {

 public Point nextPoint()
 {
       //do some action here to return a point

 }

}

//Once that is done

AClass = new AClass(); // which can be passed into that constructor. This should be enough to get you started.

Answer 3

您可以在Java 8中使用default关键字。

Answer 4

You could use an anonymous class declaration when you instantiate the class. new TrianglePictureFilter(new IPointGenerator { public Point newPoint{ // do something }});