# Class ElementScannerPreview<R,P>

java.lang.Object
javax.lang.model.util.AbstractElementVisitor6<R,P>
javax.lang.model.util.ElementScanner6<R,P>
javax.lang.model.util.ElementScanner7<R,P>
javax.lang.model.util.ElementScanner8<R,P>
javax.lang.model.util.ElementScanner9<R,P>
javax.lang.model.util.ElementScanner14<R,P>
javax.lang.model.util.ElementScannerPreview<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>`

@SupportedSourceVersion(RELEASE_25) public class ElementScannerPreview<R,P> extends ElementScanner14<R,P>
`ElementScannerPreview` is a reflective preview API of the Java platform.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
A scanning visitor of program elements with default behavior appropriate for a preview 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 by 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.
Since:
  23
See Also:
  - Expected visitor evolution
  - Compatibility note for subclasses
  - `ElementScanner6`
  - `ElementScanner7`
  - `ElementScanner8`
  - `ElementScanner9`
  - `ElementScanner14`

- ## Field Summary

  ### Fields declared in class ElementScanner6

  `DEFAULT_VALUE`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `ElementScannerPreview()`
  Constructor for concrete subclasses; uses `null` for the default value.
  `protected`
  `ElementScannerPreview(R defaultValue)`
  Constructor for concrete subclasses; uses the argument for the default value.

- ## Method Summary

  ### Methods declared in class ElementScanner14

  `visitExecutable, visitRecordComponent, visitType`

  ### Methods declared in class ElementScanner9

  `visitModule`

  ### Methods declared in class ElementScanner7

  `visitVariable`

  ### Methods declared in class ElementScanner6

  `scan, scan, scan, visitPackage, visitTypeParameter`

  ### Methods declared in class AbstractElementVisitor6

  `visit, visit, visitUnknown`

  ### Methods declared in class Object

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

- ## Constructor Details

  - ### ElementScannerPreview

    protected ElementScannerPreview()
    Constructor for concrete subclasses; uses `null` for the default value.

  - ### ElementScannerPreview

    protected ElementScannerPreview(R defaultValue)
    Constructor for concrete subclasses; uses the argument for the default value.
    Parameters:
      `defaultValue` - the default value