Java - abstract/interface ?

// Chci udelat "spolecnou tridu":

package tvary;

import java.awt.Color;
import java.awt.Point;

//co pouzit?
//public abstract class Usecka {
public interface Usecka {
    private int x1;
    private int y1;
    private int x2;
    private int y2;
    private Color barva;

    public Usecka(Point start, Point cil, Color barva) {
        this.x1 = start.x;
        this.y1 = start.y;
        this.x2 = cil.x;
        this.y2 = cil.y;
        this.barva = barva;
    }

    public void kresli();

}
// a ty jednotlivy usecky by ji nejak pouzivaly
/* ------------------------------------------------------------- */
package tvary;

import gui.DrawImage;
import java.awt.Color;
import java.awt.Point;

public class UseckaTrivial {
    // ty promenny tu taky nechci
    private int x1;
    private int y1;
    private int x2;
    private int y2;
    private Color barva;

    // aby tu nemusel byt kontruktor - pouzil by se ten z Usecka
    public UseckaTrivial(Point start, Point cil, Color barva) {
        this.x1 = start.x;
        this.y1 = start.y;
        this.x2 = cil.x;
        this.y2 = cil.y;
        this.barva = barva;
    }

    public void kresli() {
        // ...
    }
}