Decorator

interface Icecream{
   int getPrice();
   void printComposition();
}

class ChocoWafer implements Icecream{ //make a ChocoWafer class
    private Icecream icecream; //already made cone if any
    private int price = 20; 
    
    ChocoWafer(){} //if no cone till now
    
    ChocoWafer(Icecream icecream){ //if one cone is already there
        if(icecream == null){
            throw new NullPointerException(); 
        }
        this.icecream = icecream;
    }
    
    public int getPrice(){
        int cost = price;
        if(icecream!=null){
            cost+=icecream.getPrice();
        }
        return cost;
    }
    
    public void printComposition(){
        if(icecream != null){
            icecream.printComposition();
        }
        System.out.println(" ChocoWafer ");
    }
}

class VanilaWafer implements Icecream{ //make a ChocoWafer class
    private Icecream icecream; //already made cone if any
    private int price = 10; 
    
    VanilaWafer(){} //if no cone till now
    
    VanilaWafer(Icecream icecream){ //if one cone is already there
        if(icecream == null){
            throw new NullPointerException(); 
        }
        this.icecream = icecream;
    }
    
    public int getPrice(){
        int cost = price;
        if(icecream!=null){
            cost+=icecream.getPrice();
        }
        return cost;
    }
    
    public void printComposition(){
        if(icecream != null){
            icecream.printComposition();
        }
        System.out.println(" VanilaWafer ");
    }
}

//----------------------------------------

class ChocoScoop implements Icecream{
    private Icecream icecream; //already made cone if any
    private int price = 30; 
    
    ChocoScoop(Icecream icecream){ //if one cone is already there
        if(icecream == null){
            throw new NullPointerException(); 
        }
        this.icecream = icecream;
    }
    
    public int getPrice(){
        int cost = price;
        if(icecream!=null){
            cost+=icecream.getPrice();
        }
        return cost;
    }
    
    public void printComposition(){
        if(icecream != null){
            icecream.printComposition();
        }
        System.out.println(" ChocoScoop ");
    } 
}

class VanilaScoop implements Icecream{
    private Icecream icecream; //already made cone if any
    private int price = 20; 
    
    VanilaScoop(Icecream icecream){ //if one cone is already there
        if(icecream == null){
            throw new NullPointerException(); 
        }
        this.icecream = icecream;
    }
    
    public int getPrice(){
        int cost = price;
        if(icecream!=null){
            cost+=icecream.getPrice();
        }
        return cost;
    }
    
    public void printComposition(){
        if(icecream != null){
            icecream.printComposition();
        }
        System.out.println(" VanilaScoop ");
    } 
}

//----------------------------------------

public class MakeIcecream{
    public static void main(String[] args){
        Icecream icecream = new VanilaScoop(new ChocoScoop(new VanilaWafer(new ChocoWafer())));
        System.out.println(icecream.getPrice());
        icecream.printComposition();
    }
}

//Output
80
ChocoWafer 
VanilaWafer 
ChocoScoop 
VanilaScoop