Question

I do a condition with a value when it is null and when it is not null.
The time where this value is null I got the java.lang.NullPointerException.

How could I deal with this in order to dismiss this exception?

I need the condition when the value is null and when it is not.

Answer 1

You get a NullPointerException when you try to call a method using a variable that is null. Simple example:

String s = null;
int len = s.length();  // NullPointerException because s is null

So you should check if the variable is null before calling any method on it, for example:

int len;
if (s == null) {
    len = 0;
}
else {
    len = s.length();  // Safe, s is never null when you get here
}

Note that a NullPointerException is usually easy to solve. Carefully look at the stack trace of the exception; it tells you exactly in which line of your code the exception happens. Check what could be null in that line of code, and check if you’re calling a method on something that might be null. Add a check (or prevent that the relevant thing can ever be null in another way).