Java. Lang. nullpointerexception is generally reported for the following reasons:

Generally, java. Lang. nullpointerexception is reported for the following reasons:
· The string variable is not initialized;
· The object of the interface type is not initialized with a specific class, for example:
List lt; will report an error
List lT = new arraylist (); no error is reported
· When the value of an object is null, you are not sure whether it is null.
You can try CodeAdd a line of code before:

If (rb! = NULL );

........................ String type objects can be judged as follows if (rb! = NULL &&! "". Equals (RB ))
...... Of course, you can also make another judgment, whether it is not a Null String if (rb! = NULL &&! "". Equals (RB. Trim ()))