R - the return type of this visitor's methods. Use Void for visitors that do not need to return results.P - the type of the additional parameter to this visitor's methods. Use Void for visitors that do not need an additional parameter.public interface ElementVisitor<R,P>
A visitor of program elements, in the style of the visitor design pattern. Classes implementing this interface are used to operate on an element when the kind of element is unknown at compile time. When a visitor is passed to an element's accept method, the visitXYZ method most applicable to that element is invoked.
Classes implementing this interface may or may not throw a NullPointerException if the additional parameter p is null; see documentation of the implementing class for details.
WARNING: It is possible that methods will be added to this interface to accommodate new, currently unknown, language structures added to future versions of the Java™ programming language. Therefore, visitor classes directly implementing this interface may be source incompatible with future versions of the platform. To avoid this source incompatibility, visitor implementations are encouraged to instead extend the appropriate abstract visitor class that implements this interface. However, an API should generally use this visitor interface as the type for parameters, return type, etc. rather than one of the abstract classes.
Note that methods to accommodate new language constructs could be added in a source compatible way if they were added as default methods. However, default methods are only available on Java SE 8 and higher releases and the javax.lang.model.* packages bundled in Java SE 8 are required to also be runnable on Java SE 7. Therefore, default methods cannot be used when extending javax.lang.model.* to cover Java SE 8 language features. However, default methods may be used in subsequent revisions of the javax.lang.model.* packages that are only required to run on Java SE 8 and higher platform versions.
AbstractElementVisitor6, AbstractElementVisitor7
R visit(Element e,
P p) Visits an element.
e - the element to visitp - a visitor-specified parameterR visit(Element e)
A convenience method equivalent to v.visit(e, null).
e - the element to visitR visitPackage(PackageElement e,
P p) Visits a package element.
e - the element to visitp - a visitor-specified parameterR visitType(TypeElement e,
P p) Visits a type element.
e - the element to visitp - a visitor-specified parameterR visitVariable(VariableElement e,
P p) Visits a variable element.
e - the element to visitp - a visitor-specified parameterR visitExecutable(ExecutableElement e,
P p) Visits an executable element.
e - the element to visitp - a visitor-specified parameterR visitTypeParameter(TypeParameterElement e,
P p) Visits a type parameter element.
e - the element to visitp - a visitor-specified parameterR visitUnknown(Element e,
P p) Visits an unknown kind of element. This can occur if the language evolves and new kinds of elements are added to the Element hierarchy.
e - the element to visitp - a visitor-specified parameterUnknownElementException - a visitor implementation may optionally throw this exception
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