In FieldUtils replace Validate.isTrue(object != null) with Validate.notNull(object)

Methods in FieldUtils validate input using code like:

Validate.isTrue(cls != null, "The class must not be null")

This could be changed to:

Validate.notNull(cls, "The class must not be null")

However this could affect client code, since isTrue(boolean) throws IllegalArgumentException and notNull throws NullPointerException.