Set System propery to Null in Java

Question

In my unit tests I need to set the "workingDir" system property to Null.

But I can not do somesing like this, because It give me NullPointerException:

System.setProperty("workingDir", null);

How can I do it?

Answer 1

You can't set a property to have an actual null value - you can only clear it, like this:

System.clearProperty("workingDir");

Answer 2

System.setProperty() is internally implemented using a Properties object, which in turn uses the good old Hashtable. Those hashtables never let you set a null value using theput() method, so it can't really be done that way. Jon Skeet's post has the solution.