DocTreeScanner (Java SE 15 & JDK 15)
Description: declaration: module: jdk.compiler, package: com.sun.source.util, class: DocTreeScanner
Keywords: com.sun.source.util.DocTreeScanner class

Module jdk.compiler
Package com.sun.source.util

# Class DocTreeScanner<R,​P>

java.lang.Object
com.sun.source.util.DocTreeScanner<R,​P>

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

Direct Known Subclasses:
  `DocTreePathScanner`

    public class DocTreeScanner<R,​P>
    extends Object
    implements DocTreeVisitor<R,​P>

A TreeVisitor that visits all the child tree nodes. To visit nodes of a particular type, just override the corresponding visitXYZ method. Inside your method, call super.visitXYZ to visit descendant nodes.

The default implementation of the visitXYZ methods will determine a result as follows:

- If the node being visited has no children, the result will be `null`.
- If the node being visited has one child, the result will be the result of calling `scan` on that child. The child may be a simple node or itself a list of nodes.
- If the node being visited has more than one child, the result will be determined by calling `scan` each child in turn, and then combining the result of each scan after the first with the cumulative result so far, as determined by the `reduce(R, R)` method. Each child may be either a simple node of a list of nodes. The default behavior of the `reduce` method is such that the result of the visitXYZ method will be the result of the last child scanned.

Here is an example to count the number of erroneous nodes in a tree:

       class CountErrors extends DocTreeScanner<Integer,Void> {
          @Override
          public Integer visitErroneous(ErroneousTree node, Void p) {
              return 1;
          }
          @Override
          public Integer reduce(Integer r1, Integer r2) {
              return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
          }
       }

Since:
  1.8

- ## Constructor Summary

  Constructors
  Constructor | Description
  --- | ---
  `DocTreeScanner()` |

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `R` | `reduce​(R r1, R r2)` | Reduces two results into a combined result.
  `R` | `scan​(DocTree node, P p)` | Scans a single node.
  `R` | `scan​(Iterable<? extends DocTree> nodes, P p)` | Scans a sequence of nodes.
  `R` | `visitAttribute​(AttributeTree node, P p)` | Visits an AttributeTree node.
  `R` | `visitAuthor​(AuthorTree node, P p)` | Visits an AuthorTree node.
  `R` | `visitComment​(CommentTree node, P p)` | Visits a CommentTree node.
  `R` | `visitDeprecated​(DeprecatedTree node, P p)` | Visits a DeprecatedTree node.
  `R` | `visitDocComment​(DocCommentTree node, P p)` | Visits a DocCommentTree node.
  `R` | `visitDocRoot​(DocRootTree node, P p)` | Visits a DocRootTree node.
  `R` | `visitDocType​(DocTypeTree node, P p)` | Visits a DocTypeTree node.
  `R` | `visitEndElement​(EndElementTree node, P p)` | Visits an EndElementTree node.
  `R` | `visitEntity​(EntityTree node, P p)` | Visits an EntityTree node.
  `R` | `visitErroneous​(ErroneousTree node, P p)` | Visits an ErroneousTree node.
  `R` | `visitHidden​(HiddenTree node, P p)` | Visits a HiddenTree node.
  `R` | `visitIdentifier​(IdentifierTree node, P p)` | Visits an IdentifierTree node.
  `R` | `visitIndex​(IndexTree node, P p)` | Visits an IndexTree node.
  `R` | `visitInheritDoc​(InheritDocTree node, P p)` | Visits an InheritDocTree node.
  `R` | `visitLink​(LinkTree node, P p)` | Visits a LinkTree node.
  `R` | `visitLiteral​(LiteralTree node, P p)` | Visits an LiteralTree node.
  `R` | `visitOther​(DocTree node, P p)` | Visits an unknown type of DocTree node.
  `R` | `visitParam​(ParamTree node, P p)` | Visits a ParamTree node.
  `R` | `visitProvides​(ProvidesTree node, P p)` | Visits a ProvidesTree node.
  `R` | `visitReference​(ReferenceTree node, P p)` | Visits a ReferenceTree node.
  `R` | `visitReturn​(ReturnTree node, P p)` | Visits a ReturnTree node.
  `R` | `visitSee​(SeeTree node, P p)` | Visits a SeeTree node.
  `R` | `visitSerial​(SerialTree node, P p)` | Visits a SerialTree node.
  `R` | `visitSerialData​(SerialDataTree node, P p)` | Visits a SerialDataTree node.
  `R` | `visitSerialField​(SerialFieldTree node, P p)` | Visits a SerialFieldTree node.
  `R` | `visitSince​(SinceTree node, P p)` | Visits a SinceTree node.
  `R` | `visitStartElement​(StartElementTree node, P p)` | Visits a StartElementTree node.
  `R` | `visitSummary​(SummaryTree node, P p)` | Visits a SummaryTree node.
  `R` | `visitSystemProperty​(SystemPropertyTree node, P p)` | Visits a SystemPropertyTree node.
  `R` | `visitText​(TextTree node, P p)` | Visits a TextTree node.
  `R` | `visitThrows​(ThrowsTree node, P p)` | Visits a ThrowsTree node.
  `R` | `visitUnknownBlockTag​(UnknownBlockTagTree node, P p)` | Visits an UnknownBlockTagTree node.
  `R` | `visitUnknownInlineTag​(UnknownInlineTagTree node, P p)` | Visits an UnknownInlineTagTree node.
  `R` | `visitUses​(UsesTree node, P p)` | Visits a UsesTree node.
  `R` | `visitValue​(ValueTree node, P p)` | Visits a ValueTree node.
  `R` | `visitVersion​(VersionTree node, P p)` | Visits a VersionTreeTree node.

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

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

- ## Constructor Details

  - ### DocTreeScanner

    public DocTreeScanner()

- ## Method Details

  - ### scan

    public R scan​(DocTree node, P p)
    Scans a single node.
    Parameters:
      `node` - the node to be scanned
      `p` - a parameter value passed to the visit method
    Returns:
      the result value from the visit method

  - ### scan

    public R scan​(Iterable<? extends DocTree> nodes, P p)
    Scans a sequence of nodes.
    Parameters:
      `nodes` - the nodes to be scanned
      `p` - a parameter value to be passed to the visit method for each node
    Returns:
      the combined return value from the visit methods. The values are combined using the `reduce` method.

  - ### reduce

    public R reduce​(R r1, R r2)
    Reduces two results into a combined result. The default implementation is to return the first parameter. The general contract of the method is that it may take any action whatsoever.
    Parameters:
      `r1` - the first of the values to be combined
      `r2` - the second of the values to be combined
    Returns:
      the result of combining the two parameters

  - ### visitAttribute

    public R visitAttribute​(AttributeTree node, P p)
    Visits an AttributeTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitAttribute` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitAuthor

    public R visitAuthor​(AuthorTree node, P p)
    Visits an AuthorTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitAuthor` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitComment

    public R visitComment​(CommentTree node, P p)
    Visits a CommentTree node. This implementation returns `null`.
    Specified by:
      `visitComment` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitDeprecated

    public R visitDeprecated​(DeprecatedTree node, P p)
    Visits a DeprecatedTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitDeprecated` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitDocComment

    public R visitDocComment​(DocCommentTree node, P p)
    Visits a DocCommentTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitDocComment` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitDocRoot

    public R visitDocRoot​(DocRootTree node, P p)
    Visits a DocRootTree node. This implementation returns `null`.
    Specified by:
      `visitDocRoot` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitDocType

    public R visitDocType​(DocTypeTree node, P p)
    Visits a DocTypeTree node. This implementation returns `null`.
    Specified by:
      `visitDocType` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitEndElement

    public R visitEndElement​(EndElementTree node, P p)
    Visits an EndElementTree node. This implementation returns `null`.
    Specified by:
      `visitEndElement` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitEntity

    public R visitEntity​(EntityTree node, P p)
    Visits an EntityTree node. This implementation returns `null`.
    Specified by:
      `visitEntity` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitErroneous

    public R visitErroneous​(ErroneousTree node, P p)
    Visits an ErroneousTree node. This implementation returns `null`.
    Specified by:
      `visitErroneous` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitHidden

    public R visitHidden​(HiddenTree node, P p)
    Visits a HiddenTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitHidden` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitIdentifier

    public R visitIdentifier​(IdentifierTree node, P p)
    Visits an IdentifierTree node. This implementation returns `null`.
    Specified by:
      `visitIdentifier` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitIndex

    public R visitIndex​(IndexTree node, P p)
    Visits an IndexTree node. This implementation returns `null`.
    Specified by:
      `visitIndex` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitInheritDoc

    public R visitInheritDoc​(InheritDocTree node, P p)
    Visits an InheritDocTree node. This implementation returns `null`.
    Specified by:
      `visitInheritDoc` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitLink

    public R visitLink​(LinkTree node, P p)
    Visits a LinkTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitLink` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitLiteral

    public R visitLiteral​(LiteralTree node, P p)
    Visits an LiteralTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitLiteral` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitParam

    public R visitParam​(ParamTree node, P p)
    Visits a ParamTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitParam` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitProvides

    public R visitProvides​(ProvidesTree node, P p)
    Visits a ProvidesTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitProvides` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitReference

    public R visitReference​(ReferenceTree node, P p)
    Visits a ReferenceTree node. This implementation returns `null`.
    Specified by:
      `visitReference` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitReturn

    public R visitReturn​(ReturnTree node, P p)
    Visits a ReturnTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitReturn` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSee

    public R visitSee​(SeeTree node, P p)
    Visits a SeeTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSee` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSerial

    public R visitSerial​(SerialTree node, P p)
    Visits a SerialTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSerial` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSerialData

    public R visitSerialData​(SerialDataTree node, P p)
    Visits a SerialDataTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSerialData` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSerialField

    public R visitSerialField​(SerialFieldTree node, P p)
    Visits a SerialFieldTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSerialField` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSince

    public R visitSince​(SinceTree node, P p)
    Visits a SinceTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSince` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitStartElement

    public R visitStartElement​(StartElementTree node, P p)
    Visits a StartElementTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitStartElement` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitSummary

    public R visitSummary​(SummaryTree node, P p)
    Visits a SummaryTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitSummary` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning
    Since:
      10

  - ### visitSystemProperty

    public R visitSystemProperty​(SystemPropertyTree node, P p)
    Visits a SystemPropertyTree node. This implementation returns `null`.
    Specified by:
      `visitSystemProperty` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning
    Since:
      12

  - ### visitText

    public R visitText​(TextTree node, P p)
    Visits a TextTree node. This implementation returns `null`.
    Specified by:
      `visitText` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitThrows

    public R visitThrows​(ThrowsTree node, P p)
    Visits a ThrowsTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitThrows` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitUnknownBlockTag

    public R visitUnknownBlockTag​(UnknownBlockTagTree node, P p)
    Visits an UnknownBlockTagTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitUnknownBlockTag` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitUnknownInlineTag

    public R visitUnknownInlineTag​(UnknownInlineTagTree node, P p)
    Visits an UnknownInlineTagTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitUnknownInlineTag` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitUses

    public R visitUses​(UsesTree node, P p)
    Visits a UsesTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitUses` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitValue

    public R visitValue​(ValueTree node, P p)
    Visits a ValueTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitValue` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitVersion

    public R visitVersion​(VersionTree node, P p)
    Visits a VersionTreeTree node. This implementation scans the children in left to right order.
    Specified by:
      `visitVersion` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning

  - ### visitOther

    public R visitOther​(DocTree node, P p)
    Visits an unknown type of DocTree node. This can occur if the set of tags evolves and new kinds of nodes are added to the `DocTree` hierarchy. This implementation returns `null`.
    Specified by:
      `visitOther` in interface `DocTreeVisitor<R,​P>`
    Parameters:
      `node` - the node being visited
      `p` - a parameter value
    Returns:
      the result of scanning