When would you put a semicolon after a method clos

问题:

I've been programming in Java for a while, and I've just come across this syntax for the first time:

public Object getSomething(){return something;}; 

What's interesting me is the final semicolon. It doesn't seem to be causing a compiler error, and as far as I know isn't generating runtime errors, so it seems to be valid syntax. When would I use this syntax? Or is it just something that is allowed but generally not used?

回答1:

It's allowed by the grammar as a concession to harmless syntax errors, but it's not generally used and doesn't mean anything different (than leaving the semicolon out).

Just as a }; inside a method (such as after an if block) is a null statement and is allowed, an errant semicolon outside a method is considered a null declaration and is allowed.

Specifically, the following production from the Java Language Specification allows this:

ClassBodyDeclaration:
  ; 
  [static] Block
  ModifiersOpt MemberDecl

回答2:

It's simply an empty statement - it is most likely a typo.

Consider the fact that in all C-based languages, a statement is terminated with a semicolon. A hanging semicolon like this simply terminates the current statement which in this case is nothing.

回答3:

Or is it just something that is allowed but generally not used?

Yeap, that's it. It is valid Java but doesn't do anything:

public class X  {
    ;;;;;;;;;;;;;;;;;;
    ;;;;;
    ;
}