Java Traits

Bootstrap.java

import io.liechti.traittest.Kreis;

public class Bootstrap {

    public static void main(String[] args)
    {
        init();
    }

    protected static void init()
    {
        Kreis kreis = new Kreis(30, true);
        System.out.println("Should be visible: " + kreis.isVisible());
        kreis.scaleRadiusBy(10);
        System.out.println("Should be 40: " + kreis.getRadius());
        kreis.hide();
        System.out.println("Should NOT be visible: " + kreis.isVisible());
    }
}

Hideable.java

package io.liechti.traittest;

public interface Hideable {
    void setVisible(boolean hide);
    boolean isVisible();

    default void show(){
        this.setVisible(true);
    }

    default void hide(){
        this.setVisible(false);
    }
}

Kreis.java

package io.liechti.traittest;

public class Kreis implements Hideable, Rezisable{

    private double radius = 0;
    private boolean visible = false;

    public Kreis(){
    }

    public Kreis (double radius, boolean visible){
        this.radius = radius;
    }

    @Override
    public void setVisible(boolean isVisible) {
        this.visible = isVisible;
    }

    @Override
    public boolean isVisible() {
        return this.visible;
    }

    @Override
    public void setRadius(double radius) {
        this.radius = radius;
    }

    @Override
    public double getRadius() {
        return this.radius;
    }

}

Rezisable.java

package io.liechti.traittest;

public interface Rezisable {

    void setRadius(double radius);
    double getRadius();

    /**
     * @param amount
     */
    default void shrinkRadiusBy(double amount){
        double radius = this.getRadius();
        radius -= amount;
        if(radius > 0) {
            this.setRadius(radius);
        }
    }

    /**
     * @param amount
     */
    default void scaleRadiusBy(double amount){
        double radius = this.getRadius();
        radius += amount;
        this.setRadius(radius);
    }
}