I have reminiscence that the general rule is that unless otherwise stated methods and constructors will throw NPE if passed null argument.
Unfortunately I have not found more general place in javadoc stating this except following citing from java.util.logging package description: "In general, unless otherwise noted in the javadoc, methods and contructors will throw NullPointerException if passed a null argument. The one broad exception to this rule is that the logging convenience methods in the Logger class (the config, entering, exiting, fine, finer, finest, log, logp, logrb, severe, throwing, and warning methods) will accept null values for all arguments except for the initial Level argument (if any)." I understand this as that in general methods and constructors do not check if arguments passed are null or not, otherwise javadoc specifies the exact behavior. Of course there are exceptions which are not stated in javadoc, but those exceptions should be checked on case by case basis. Also I think that exact checks for null arguments are not necessary (except those cases when they have special meaning) and moreover could cause performance impact. -- Nikolay Kuznetsov, Intel Middleware Products Division
