ElementScanner6 (Java SE 15 & JDK 15)
Description: declaration: module: java.compiler, package: javax.lang.model.util, class: ElementScanner6
Keywords: javax.lang.model.util.ElementScanner6 class

Module java.compiler
Package javax.lang.model.util

# Class ElementScanner6<R,​P>

java.lang.Object
javax.lang.model.util.AbstractElementVisitor6<R,​P>
javax.lang.model.util.ElementScanner6<R,​P>

Type Parameters:
  `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.

All Implemented Interfaces:
  `ElementVisitor<R,​P>`

Direct Known Subclasses:
  `ElementScanner7`

    @SupportedSourceVersion(RELEASE_6)
    public class ElementScanner6<R,​P>
    extends AbstractElementVisitor6<R,​P>

A scanning visitor of program elements with default behavior appropriate for the `RELEASE_6` source version. The `visitXyz` methods in this class scan their component elements by calling `scan` on their enclosed elements, parameters, etc., as indicated in the individual method specifications. A subclass can control the order elements are visited by overriding the `visitXyz` methods. Note that clients of a scanner may get the desired behavior be invoking `v.scan(e, p)` rather than `v.visit(e, p)` on the root objects of interest.

When a subclass overrides a `visitXyz` method, the new method can cause the enclosed elements to be scanned in the default way by calling `super.visitXyz`. In this fashion, the concrete visitor can control the ordering of traversal over the component elements with respect to the additional processing; for example, consistently calling `super.visitXyz` at the start of the overridden methods will yield a preorder traversal, etc. If the component elements should be traversed in some other order, instead of calling `super.visitXyz`, an overriding visit method should call `scan` with the elements in the desired order.

API Note:
  Methods in this class may be overridden subject to their general contract.

  WARNING: The `ElementVisitor` interface implemented by this class may have methods added to it in the future to accommodate new, currently unknown, language structures added to future versions of the Java programming language. Therefore, methods whose names begin with `"visit"` may be added to this class in the future; to avoid incompatibilities, classes which extend this class should not declare any instance methods with names beginning with `"visit"`.

  When such a new visit method is added, the default implementation in this class will be to directly or indirectly call the `visitUnknown` method. A new element scanner visitor class will also be introduced to correspond to the new language level; this visitor will have different default behavior for the visit method in question. When a new visitor is introduced, portions of this visitor class may be deprecated, including its constructors.

Since:
  1.6
See Also:
  `ElementScanner7`, `ElementScanner8`, `ElementScanner9`, `ElementScanner14`

- ## Field Summary

  Fields
  Modifier and Type | Field | Description
  --- | --- | ---
  `protected R` | `DEFAULT_VALUE` | The specified default value.

- ## Constructor Summary

  Constructors
  Modifier | Constructor | Description
  --- | --- | ---
  `protected` | `ElementScanner6()` | Deprecated. Release 6 is obsolete; update to a visitor for a newer release level.
  `protected` | `ElementScanner6​(R defaultValue)` | Deprecated. Release 6 is obsolete; update to a visitor for a newer release level.

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `R` | `scan​(Iterable<? extends Element> iterable, P p)` | Iterates over the given elements and calls `scan(Element, P)` on each one.
  `R` | `scan​(Element e)` | Convenience method equivalent to `v.scan(e, null)`.
  `R` | `scan​(Element e, P p)` | Processes an element by calling `e.accept(this, p)`; this method may be overridden by subclasses.
  `R` | `visitExecutable​(ExecutableElement e, P p)` | Visits an executable element.
  `R` | `visitPackage​(PackageElement e, P p)` | Visits a package element.
  `R` | `visitType​(TypeElement e, P p)` | Visits a type element.
  `R` | `visitTypeParameter​(TypeParameterElement e, P p)` | Visits a type parameter element.
  `R` | `visitVariable​(VariableElement e, P p)` | Visits a variable element.

  ### Methods declared in class javax.lang.model.util.AbstractElementVisitor6

  `visit, visit, visitModule, visitRecordComponent, visitUnknown`

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### DEFAULT_VALUE

    protected final R DEFAULT_VALUE
    The specified default value.

- ## Constructor Details

  - ### ElementScanner6

    @Deprecated(since="9") protected ElementScanner6()
    Deprecated.
    Release 6 is obsolete; update to a visitor for a newer release level.
    Constructor for concrete subclasses; uses `null` for the default value.

  - ### ElementScanner6

    @Deprecated(since="9") protected ElementScanner6​(R defaultValue)
    Deprecated.
    Release 6 is obsolete; update to a visitor for a newer release level.
    Constructor for concrete subclasses; uses the argument for the default value.
    Parameters:
      `defaultValue` - the default value

- ## Method Details

  - ### scan

    public final R scan​(Iterable<? extends Element> iterable, P p)
    Iterates over the given elements and calls `scan(Element, P)` on each one. Returns the result of the last call to `scan` or `DEFAULT_VALUE` for an empty iterable.
    Parameters:
      `iterable` - the elements to scan
      `p` - additional parameter
    Returns:
      the scan of the last element or `DEFAULT_VALUE` if no elements

  - ### scan

    public R scan​(Element e, P p)
    Processes an element by calling `e.accept(this, p)`; this method may be overridden by subclasses.
    Parameters:
      `e` - the element to scan
      `p` - a scanner-specified parameter
    Returns:
      the result of visiting `e`.

  - ### scan

    public final R scan​(Element e)
    Convenience method equivalent to `v.scan(e, null)`.
    Parameters:
      `e` - the element to scan
    Returns:
      the result of scanning `e`.

  - ### visitPackage

    public R visitPackage​(PackageElement e, P p)
    Visits a package element.
    Implementation Requirements:
      This implementation scans the enclosed elements.
    Parameters:
      `e` - the element to visit
      `p` - a visitor-specified parameter
    Returns:
      the result of scanning

  - ### visitType

    public R visitType​(TypeElement e, P p)
    Visits a type element.
    Implementation Requirements:
      This implementation scans the enclosed elements. Note that type parameters are not scanned by this implementation since type parameters are not considered to be enclosed elements of a type.
    Parameters:
      `e` - the element to visit
      `p` - a visitor-specified parameter
    Returns:
      the result of scanning

  - ### visitVariable

    public R visitVariable​(VariableElement e, P p)
    Visits a variable element.
    Implementation Requirements:
      This implementation scans the enclosed elements, unless the element is a `RESOURCE_VARIABLE` in which case `visitUnknown` is called.
    Parameters:
      `e` - the element to visit
      `p` - a visitor-specified parameter
    Returns:
      the result of scanning

  - ### visitExecutable

    public R visitExecutable​(ExecutableElement e, P p)
    Visits an executable element.
    Implementation Requirements:
      This implementation scans the parameters. Note that type parameters are not scanned by this implementation.
    Parameters:
      `e` - the element to visit
      `p` - a visitor-specified parameter
    Returns:
      the result of scanning

  - ### visitTypeParameter

    public R visitTypeParameter​(TypeParameterElement e, P p)
    Visits a type parameter element.
    Implementation Requirements:
      This implementation scans the enclosed elements.
    Parameters:
      `e` - the element to visit
      `p` - a visitor-specified parameter
    Returns:
      the result of scanning