Valid Keywords for Beginning a Java Source File

Question

So far I know that these keywords are valid for beginning a java source file:

class, public, import, package, interface, and final

Additions from comments: abstract, strictfp, enum

Are there any more?

(Thanks for all the super quick responses! Feel free to edit this to add more that are found.)

Answer 1

How about enum ?

How about private ?

EDIT: Okay, that was my stupid blurt-out of the day.

Answer 2

Don't forget abstract

Answer 3

abstract

Answer 4

Annotations are valid http://java.sun.com/j2se/1.5.0/docs/guide/language/annotations.html

Examples

• @Preliminary @Copyright("2002 Yoyodyne Propulsion Systems")
• @Retention(RetentionPolicy.RUNTIME)
• @Target(ElementType.METHOD)

Answer 5

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 the JLS §8.1.1:

A class declaration may include class modifiers.

ClassModifiers:
    ClassModifier
    ClassModifiers ClassModifier

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

Not all modifiers are applicable to all kinds of class declarations. The access modifier public pertains only to top level classes (§7.6) and to member classes (§8.5, §9.5), and is discussed in §6.6, §8.5 and §9.5. The access modifiers protected and private pertain only to member classes within a directly enclosing class declaration (§8.5) and are discussed in §8.5.1. The access modifier static pertains only to member classes (§8.5, §9.5). A compile-time error occurs if the same modifier appears more than once in a class declaration.

Answer 6

Don't forget static and protected and javaDoc comments

Answer 7

• Real modifiers you missed: abstract, strictfp

• Annotations like @Retention

• Annotation declarations: @interface

• Enumeration: enum

• Comments and whitespace

• As far as I know, nothing else

• Keep in mind that identifiers may use unicode escapes inside them, like cl\u0061ss

Answer 8

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

You should start with CompilationUnit.

Answer 9

For Java > 1.5, enum as well. As others mentionned, abstract.

Answer 10

Looking through the keyword list, and a modifier matrix now you only miss strictfp.

Answer 11

module. In JDK7. Perhaps. (Technically not a real keyword.)

(And is an empty file valid? As package-info.java? It's not really an interesting enough question for me to bother finding out.)