Type Witness in java generics

Question

I understand what Type Witness is as I see from Generics Trail In Java Documentation

BoxDemo.addBox(Integer.valueOf(10), listOfIntegerBoxes);
         


        

Answer 1

For completeness, this was added in Java 5. Here are the relevant parts of JLS Third Edition, which covers Java 5 and 6:

8.8.7.1 Explicit Constructor Invocations

ExplicitConstructorInvocation:
    NonWildTypeArgumentsopt this ( ArgumentListopt ) ;
    NonWildTypeArgumentsopt super ( ArgumentListopt ) ;
    Primary. NonWildTypeArgumentsopt super ( ArgumentListopt ) ; 

NonWildTypeArguments:
    < ReferenceTypeList >

ReferenceTypeList: 
    ReferenceType
    ReferenceTypeList , ReferenceType

15.12 Method Invocation Expressions

MethodInvocation:
    MethodName ( ArgumentListopt )
    Primary . NonWildTypeArgumentsopt Identifier ( ArgumentListopt )
    super . NonWildTypeArgumentsopt Identifier ( ArgumentListopt )
    ClassName . super . NonWildTypeArgumentsopt Identifier ( ArgumentListopt )
    TypeName . NonWildTypeArguments Identifier ( ArgumentListopt )

Note they are called NonWildTypeArguments. The term "Type Witness" does not appear in the JLS. In JLS SE 8, the invocation specs are rewritten to use the pre-existing notion of TypeArguments; and the word "witness" still appears nowhere.

(MethodName already includes TypeName.Identifier, so that fifth method invocation defines the explicit usage of a Type Witness, which is why it is not marked optional.)