Escape :
I would like to apply icons to my program, but it gives me an error. It looks all good, that is why I dont have a clue what is wrong with it.
public static ImageIcon createIcon (String path) {
URL url = System.class.getResource(path);
if(url == null) {
System.err.println("Unable to load image: " + path);
}
ImageIcon icon = new ImageIcon(url); //here is line 30 in class Utils
return icon;
}
And his is the error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.desktop/javax.swing.ImageIcon.<init>(ImageIcon.java:217)
at gui.Utils.createIcon(Utils.java:30)
Arvind Kumar Avinash :
The problem is that url is null. Check how the constructor has been implemented:
public ImageIcon (URL location) {
this(location, location.toExternalForm());
}
If location is null, location.toExternalForm() will throw NullPointerException.
In fact, if path is null, that too can cause NullPointerException. See how getResource has been implemented.
public URL getResource(String name) {
name = resolveName(name);
//...
}
private String resolveName(String name) {
if (!name.startsWith("/")) {
Class<?> c = this;
while (c.isArray()) {
c = c.getComponentType();
}
String baseName = c.getPackageName();
if (baseName != null && !baseName.isEmpty()) {
name = baseName.replace('.', '/') + "/" + name;
}
} else {
name = name.substring(1);
}
return name;
}
As you can see, if name is null, name.startsWith("/") will throw NullPointerException.
Do it as follows:
public static ImageIcon createIcon (String path) {
if(path == null) {
System.err.println("Path is null");
return null;
}
URL url = System.class.getResource(path);
ImageIcon icon = null;
if(url != null) {
icon = new ImageIcon(url);
} else {
System.err.println("Unable to load image: " + path);
}
return icon;
}
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