Optimizing method in Java

Pass in a Supplier of the type you want to create:

public <T extends Sprite> void addThings(List<? super T> list, Supplier<T> supplier) { 

And then replace the constructor with an invocation of that supplier:

T thing = supplier.get(); imageWidth = thing.getWidth(); pane.getChildren().add(thing); list.add(thing); 

You would invoke this something like:

addThings(listOfDragons, Dragon::new); addThings(listOfOrcs, Orc::new); 

Considering your class Structure is like this

public interface Entity { // abstract methods here } public class Orc implements Entity { //Code here } public class Dragon implements Entity { //Code here } 

now modify your method as below

 public <T extends Entity> void addDragon(List<T> list, Class<T> clazz) throws IllegalAccessException, InstantiationException { double imageWidth = 0; for(int i = 0; i < 6; i++) { T enemy = clazz.newInstance(); imageWidth = enemy.getWidth(); pane.getChildren().add(enemy); list.add(enemy); } } 

Here < T extends Entity > makes your method flexible to be called by passing any class which are implementing Enemies.

Generic might help you

public <T extends Entity> void addEntity(List<T> list, Class<T> clazz) { double imageWidth = 0; for(int i = 0; i < 6; i++) { T entity = clazz.newInstance(); imageWidth = entity.getWidth(); pane.getChildren().add(entity); list.add(entity); } } 

Add an interface, or add methods to Entity, for the things you need to do to all entities. This would include a factory method to create a new instance of the specific subtype, and getWidth. Call addEnemy with a prototype instance of the type to be added.

public void addEnemy(List<Entity> list,Entity enemy) { double imageWidth = 0; for(int i = 0; i < 6; i++) { Entity someEnemy = enemy.createNewInstance(); imageWidth = someEnemy .getWidth(); pane.getChildren().add(someEnemy ); list.add(someEnemy ); } 

}