Question

I created a constructor with Javassist which has no real method

CtConstructor c = CtNewConstructor.make ( argTypes, null, newClass );

When I’m trying to put out the signature of this class

c.getSignature();

I get

public Echo ()V

I’m confused what “V” means? I expected either public Echo (); or something similar…

Answer 1

The JVM uses a compact way of storing method signatures, of which constructors are considered a special case.

For your example:

• () indicates a method taking no arguments
• V indicates that it returns nothing

The other parts of the scheme are:

• B – byte
• C – char
• D – double
• F – float
• I – int
• J – long
• S – short
• V – void
• Z – boolean
• [ – array of the thing following the bracket
• L [class name] ; – instance of this class, with dots becoming slashes
• ( [args] ) [return type] – method signature

For example:

public int foo(String bar, long[][] baz)

would become

(Ljava/lang/String;[[J)I

See the spec at Sun^H^H^HOracle’s web site