Set System propery to Null in Java

问题

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?

回答1:

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

System.clearProperty("workingDir");

回答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.

回答3:

You can't do it, as setProperty method throws NullPointerException if any of it's arguments is null. You can put an empty string there and check for it in your unit tests or simply clearProperty, as Jon suggested.

来源：https://stackoverflow.com/questions/4323995/set-system-propery-to-null-in-java