Valid keywords to start Java source file

How about enum

?

How about private

?

EDIT: Ok, that was my stupid rebuke from the day.

abstract

For the Java> 1.5, . As others have noted . enum

abstract

Viewing the list of keywords and modifier matrix now you just skip strictfp.

Also from http://java.sun.com/j2se/1.5.0/docs/guide/language/annotations.html don't forget @interface

!

Edit: Also strictfp

applies to classes. See JLS §8.1.1 :

A class declaration can include class modifiers.

ClassModifiers:
    ClassModifier
    ClassModifiers ClassModifier

ClassModifier: one of
    Annotation public protected private
    abstract static final strictfp 

Not all modifiers apply to all kinds of class declarations. The access modifier public

only applies to top-level classes (§7.6) and member classes (§8.5, §9.5) and is discussed in §6.6, §8.5, and §9.5. Access modifiers protected

and private

are only relevant to member classes in a directly nested class declaration (§8.5) and are discussed in section 8.5. The access modifier static

only applies to member classes (§8.5, §9.5). A compile-time error occurs if the same modifier appears more than once in a class declaration.

You should take a look at The Grammar of the Java Programming Language . From there, you can enclose all possible keywords.

You must start with CompilationUnit.

module

... In JDK7. May be. (Technically not a real keyword.)

(And is the empty file valid? How package-info.java

? It's not a very interesting question for me to ask about.)