getClass() returning null but Foo.class working

Question

When using the following I get a NullPointerException:

Class clazz = Foo.class;
String path = new File(clazz.getClass().getProtectionDomain().getCodeSource().getLocation().toURI().getPath()) + "";

However, it works when I use:

String path = new File(Foo.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath()) + "";

Is there any way around the NullPointerException?

Why do you call `getClass` on a `Class` instance? Do you really want to have the java class of java's `Class`? — isnot2bad, Mar 30 '15 at 14:27
`Foo.class` already is a `Class`. Don't call `getClass()` on it! — isnot2bad, Mar 30 '15 at 14:33

score 3 · Answer 1 · answered Mar 30 '15 at 14:27

3

You should call getClass() on an instance of a class.

MyClass myClassInstance = new MyClass();
Class clazz = myClassInstance.getClass();

You are trying to call it on the class Object

answered Mar 30 '15 at 14:27

TheLostMind

This still returns `NullPointerException` – tank Mar 30 '15 at 14:30
@tank - You will have to check which method in that chain is returning `null`. – TheLostMind Mar 30 '15 at 14:32

score 1 · Accepted Answer · answered Mar 30 '15 at 14:30

1

You don't have to invoke getClass on your clazz or you will get the Class.class instead of Foo.class.

So it should be:

Class clazz = Foo.class;
String path = new File(clazz.getProtectionDomain().getCodeSource().getLocation().toURI().getPath()) + "";

answered Mar 30 '15 at 14:30

Stefaan Neyts

score 0 · Answer 3 · edited May 23 '17 at 12:06

0

It depends on how the class was loaded - like for instance if the class was loaded from the Bootstrap classloader.

See here for a more complete answer.

edited May 23 '17 at 12:06

Community

answered Mar 30 '15 at 14:39

OldCurmudgeon

3 Answers3