Question

I have a number of icons used throughout an application – let’s take ok/cancel icons as an example. At the moment they might be a tick and a cross (tick.png, cross.png) but I may want to replace them in future. Also, I would like to keep the resource path in one place.

Is this ok:

public class Icons {     public static Icon OK = new ImageIcon(Icons.class.getResource('/icons/tick.png');     public static Icon CANCEL = new ImageIcon(Icons.class.getResource('/icons/cross.png'); } 

Or should I be doing this a different way? I don’t mind relying on the existence of the image files at runtime since they’re in the .jar

Solution

I’ve used Bent’s idea for initialisation, and I’ve made the constants final:

public final class Icons {     private static final Logger logger = Logger.getLogger(Icons.class);      public static final Icon OK = icon('/icons/add.png');     public static final Icon CANCEL = icon('/icons/cancel.png');      private static Icon icon(String path) {         URL resource = Icons.class.getResource(path);         if(resource==null) {             logger.error('Resource '+path+' does not exist');             return new ImageIcon();         }         return new ImageIcon(resource);     } } 

Answer 1

If you want to keep you icons as static constants, I would extract the instantiation of the ImageIcon objects into a static method;

public static final Icon ok = icon('ok.png');   private static Icon icon(String path) {      URL resource = Icons.class.getResource('/icons/' + path);     if (resource == null) {         // Log something...         return null;     }     return new ImageIcon(resource); } 

This way you have control whenever something fail, and you don’t have to repeat yourself in the instantiation.

Also, I would make the constants final.

A more general approach could be to use reflection to inspect your Icons-class and load resources for each public static Icon field in the class. This way, you would only have to declare a new Icon constant, and the corresponding resource would be loaded automatically based on the name of the constant. Leave a comment if you want more tips for doing this.