Proxy

//Object interface
public interface Image{
    public void display();
}


//Real object
public class RealImage implements Image {
    private String file;

    public RealImage(String fileName){
        this.file = fileName;
        loadImageFromDisk();
    }
    @Override
    public void display(){
        System.out.println("Rendering image : "+ file);
    }
    private void loadImageFromDisk(){
        System.out.println("Loading image "+file+" from disk");
    }
}

//Proxy class
public class ProxyImage implements Image {
    private Image image;
    private String file;

    public ProxyImage(String fileName){
        this.file =fileName;
    }
    @Override
    public void display(){
        if(image ==null){// create object of RealImage only if the image reference is null, thus resulting in LazyIntialization 
            //( i.e. Initializing the object only when it is needed not beforehand)
            image = new RealImage(file);
        }
        image.display();
    }

}

// client
public class Main {
    public static void main(String args[]){
        Image image = new ProxyImage("wallpaper.png");
        //image is loaded and displayed for the first time
        image.display();
        //image will not be loaded again, only display will be called 
        image.display();
    }
}

Loading image wallpaper.png from disk
Rendering image : wallpaper.png