Current format is:
[FullTypeName DOT] Ident LPAREN [FullTypeName ParamName {COMMA FullTypeName ParamName} [COMMA FullTypeName ELLIPSIS ParamName]] RPAREN

There are some problems:
1. No return type
    Return type is one of the important things when we think about methods.

2. No type parameters
    When the parameter types is the type parameter, the documentation is difficult to understand:

    java.util.Optional.of(T arg0) // what is T? what is the bound of T?

3. No thrown type
4. ParamName is useless
    Because it is always arg0, arg1, arg2, ..., argN.
5. FullTypeName is too verbose.
    The class name is not simplified even if it is already imported.

I propose the following format:
    Documentation = Constructor | Method
        Constructor = ConstructorName Arguments ThrowsOpt
            ConstructorName = [TypeParameters] SimplifiedType
            Arguments = LPAREN [SimplifiedType {COMMA SimplifiedType} [COMMA SimplifiedType ELLIPSIS]] RPAREN
            ThworsOpt = [THROWS SimplifiedType {COMMA SimplifiedType}]
        Method = ReturnType MethodName Arguments ThrowsOpt
            ReturnType = SimplifiedType
            MethodName = [SimplifiedType DOT] [TypeParameters] Ident

SimplifiedType is simplified by SnippetMaps#fullClassNameAndPackageToClass and with TypeParameter.

Ex:
void printf(String, Object...)

void f(List<String>, Function<? super String,? extends String>)
(when j.u.List, j.u.f.Function are imported)