Class TreeScanner<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:
TreeVisitor<R,​P>
Direct Known Subclasses:
TreePathScanner
public class TreeScanner<R,P>
extends Object
implements TreeVisitor<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 identifier nodes in a tree: 

class CountIdentifiers extends TreeScanner<Integer,Void> {
      @Override
      public Integer visitIdentifier(IdentifierTree node, Void p) {
          return 1;
      }
      @Override
      public Integer reduce(Integer r1, Integer r2) {
          return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
      }
   }
Since:
1.6

Constructors

Constructor Description
TreeScanner()

Methods

Modifier and Type Method Description
R reduce​(R r1, R r2)

Reduces two results into a combined result.
R scan​(Tree tree, P p)

Scans a single node.
R scan​(Iterable<? extends Tree> nodes, P p)

Scans a sequence of nodes.
R visitAnnotatedType​(AnnotatedTypeTree node, P p)

Visits an AnnotatedTypeTree node.
R visitAnnotation​(AnnotationTree node, P p)

Visits an AnnotatedTree node.
R visitArrayAccess​(ArrayAccessTree node, P p)

Visits an ArrayAccessTree node.
R visitArrayType​(ArrayTypeTree node, P p)

Visits an ArrayTypeTree node.
R visitAssert​(AssertTree node, P p)

Visits an AssertTree node.
R visitAssignment​(AssignmentTree node, P p)

Visits an AssignmentTree node.
R visitBinary​(BinaryTree node, P p)

Visits a BinaryTree node.
R visitBlock​(BlockTree node, P p)

Visits a BlockTree node.
R visitBreak​(BreakTree node, P p)

Visits a BreakTree node.
R visitCase​(CaseTree node, P p)

Visits a CaseTree node.
R visitCatch​(CatchTree node, P p)

Visits a CatchTree node.
R visitClass​(ClassTree node, P p)

Visits a ClassTree node.
R visitCompilationUnit​(CompilationUnitTree node, P p)

Visits a CompilationUnitTree node.
R visitCompoundAssignment​(CompoundAssignmentTree node, P p)

Visits a CompoundAssignmentTree node.
R visitConditionalExpression​(ConditionalExpressionTree node, P p)

Visits a ConditionalExpressionTree node.
R visitContinue​(ContinueTree node, P p)

Visits a ContinueTree node.
R visitDoWhileLoop​(DoWhileLoopTree node, P p)

Visits a DoWhileTree node.
R visitEmptyStatement​(EmptyStatementTree node, P p)

Visits an EmptyStatementTree node.
R visitEnhancedForLoop​(EnhancedForLoopTree node, P p)

Visits an EnhancedForLoopTree node.
R visitErroneous​(ErroneousTree node, P p)

Visits an ErroneousTree node.
R visitExpressionStatement​(ExpressionStatementTree node, P p)

Visits an ExpressionStatementTree node.
R visitForLoop​(ForLoopTree node, P p)

Visits a ForLoopTree node.
R visitIdentifier​(IdentifierTree node, P p)

Visits an IdentifierTree node.
R visitIf​(IfTree node, P p)

Visits an IfTree node.
R visitImport​(ImportTree node, P p)

Visits an ImportTree node.
R visitInstanceOf​(InstanceOfTree node, P p)

Visits an InstanceOfTree node.
R visitIntersectionType​(IntersectionTypeTree node, P p)

Visits an IntersectionTypeTree node.
R visitLabeledStatement​(LabeledStatementTree node, P p)

Visits a LabeledStatementTree node.
R visitLambdaExpression​(LambdaExpressionTree node, P p)

Visits a LambdaExpressionTree node.
R visitLiteral​(LiteralTree node, P p)

Visits a LiteralTree node.
R visitMemberReference​(MemberReferenceTree node, P p)

Visits a MemberReferenceTree node.
R visitMemberSelect​(MemberSelectTree node, P p)

Visits a MemberSelectTree node.
R visitMethod​(MethodTree node, P p)

Visits a MethodTree node.
R visitMethodInvocation​(MethodInvocationTree node, P p)

Visits a MethodInvocationTree node.
R visitModifiers​(ModifiersTree node, P p)

Visits a ModifiersTree node.
R visitNewArray​(NewArrayTree node, P p)

Visits a NewArrayTree node.
R visitNewClass​(NewClassTree node, P p)

Visits a NewClassTree node.
R visitOther​(Tree node, P p)

Visits an unknown type of Tree node.
R visitPackage​(PackageTree node, P p)

Visits a PackageTree node.
R visitParameterizedType​(ParameterizedTypeTree node, P p)

Visits a ParameterizedTypeTree node.
R visitParenthesized​(ParenthesizedTree node, P p)

Visits a ParenthesizedTree node.
R visitPrimitiveType​(PrimitiveTypeTree node, P p)

Visits a PrimitiveTypeTree node.
R visitReturn​(ReturnTree node, P p)

Visits a ReturnTree node.
R visitSwitch​(SwitchTree node, P p)

Visits a SwitchTree node.
R visitSynchronized​(SynchronizedTree node, P p)

Visits a SynchronizedTree node.
R visitThrow​(ThrowTree node, P p)

Visits a ThrowTree node.
R visitTry​(TryTree node, P p)

Visits a TryTree node.
R visitTypeCast​(TypeCastTree node, P p)

Visits a TypeCastTree node.
R visitTypeParameter​(TypeParameterTree node, P p)

Visits a TypeParameterTree node.
R visitUnary​(UnaryTree node, P p)

Visits a UnaryTree node.
R visitUnionType​(UnionTypeTree node, P p)

Visits a UnionTypeTree node.
R visitVariable​(VariableTree node, P p)

Visits a VariableTree node.
R visitWhileLoop​(WhileLoopTree node, P p)

Visits a WhileLoopTree node.
R visitWildcard​(WildcardTree node, P p)

Visits a WildcardTypeTree node.

Methods declared in class java.lang.Object

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

Methods declared in interface com.sun.source.tree.TreeVisitor

visitExports, visitModule, visitOpens, visitProvides, visitRequires, visitUses

Constructors

TreeScanner

public TreeScanner()

Methods

scan

public R scan(Tree tree,
              P p)

Scans a single node.

Parameters:
tree - 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 Tree> 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

visitCompilationUnit

public R visitCompilationUnit(CompilationUnitTree node,
                              P p)

Visits a CompilationUnitTree node. This implementation scans the children in left to right order.

Specified by:
visitCompilationUnit in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitPackage

public R visitPackage(PackageTree node,
                      P p)

Visits a PackageTree node. This implementation scans the children in left to right order.

Specified by:
visitPackage in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitImport

public R visitImport(ImportTree node,
                     P p)

Visits an ImportTree node. This implementation scans the children in left to right order.

Specified by:
visitImport in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitClass

public R visitClass(ClassTree node,
                    P p)

Visits a ClassTree node. This implementation scans the children in left to right order.

Specified by:
visitClass in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitMethod

public R visitMethod(MethodTree node,
                     P p)

Visits a MethodTree node. This implementation scans the children in left to right order.

Specified by:
visitMethod in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitVariable

public R visitVariable(VariableTree node,
                       P p)

Visits a VariableTree node. This implementation scans the children in left to right order.

Specified by:
visitVariable in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitEmptyStatement

public R visitEmptyStatement(EmptyStatementTree node,
                             P p)

Visits an EmptyStatementTree node. This implementation returns null.

Specified by:
visitEmptyStatement in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitBlock

public R visitBlock(BlockTree node,
                    P p)

Visits a BlockTree node. This implementation scans the children in left to right order.

Specified by:
visitBlock in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitDoWhileLoop

public R visitDoWhileLoop(DoWhileLoopTree node,
                          P p)

Visits a DoWhileTree node. This implementation scans the children in left to right order.

Specified by:
visitDoWhileLoop in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitWhileLoop

public R visitWhileLoop(WhileLoopTree node,
                        P p)

Visits a WhileLoopTree node. This implementation scans the children in left to right order.

Specified by:
visitWhileLoop in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitForLoop

public R visitForLoop(ForLoopTree node,
                      P p)

Visits a ForLoopTree node. This implementation scans the children in left to right order.

Specified by:
visitForLoop in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitEnhancedForLoop

public R visitEnhancedForLoop(EnhancedForLoopTree node,
                              P p)

Visits an EnhancedForLoopTree node. This implementation scans the children in left to right order.

Specified by:
visitEnhancedForLoop in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitLabeledStatement

public R visitLabeledStatement(LabeledStatementTree node,
                               P p)

Visits a LabeledStatementTree node. This implementation scans the children in left to right order.

Specified by:
visitLabeledStatement in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitSwitch

public R visitSwitch(SwitchTree node,
                     P p)

Visits a SwitchTree node. This implementation scans the children in left to right order.

Specified by:
visitSwitch in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitCase

public R visitCase(CaseTree node,
                   P p)

Visits a CaseTree node. This implementation scans the children in left to right order.

Specified by:
visitCase in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitSynchronized

public R visitSynchronized(SynchronizedTree node,
                           P p)

Visits a SynchronizedTree node. This implementation scans the children in left to right order.

Specified by:
visitSynchronized in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitTry

public R visitTry(TryTree node,
                  P p)

Visits a TryTree node. This implementation scans the children in left to right order.

Specified by:
visitTry in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitCatch

public R visitCatch(CatchTree node,
                    P p)

Visits a CatchTree node. This implementation scans the children in left to right order.

Specified by:
visitCatch in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitConditionalExpression

public R visitConditionalExpression(ConditionalExpressionTree node,
                                    P p)

Visits a ConditionalExpressionTree node. This implementation scans the children in left to right order.

Specified by:
visitConditionalExpression in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitIf

public R visitIf(IfTree node,
                 P p)

Visits an IfTree node. This implementation scans the children in left to right order.

Specified by:
visitIf in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitExpressionStatement

public R visitExpressionStatement(ExpressionStatementTree node,
                                  P p)

Visits an ExpressionStatementTree node. This implementation scans the children in left to right order.

Specified by:
visitExpressionStatement in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitBreak

public R visitBreak(BreakTree node,
                    P p)

Visits a BreakTree node. This implementation returns null.

Specified by:
visitBreak in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitContinue

public R visitContinue(ContinueTree node,
                       P p)

Visits a ContinueTree node. This implementation returns null.

Specified by:
visitContinue in interface TreeVisitor<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 TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitThrow

public R visitThrow(ThrowTree node,
                    P p)

Visits a ThrowTree node. This implementation scans the children in left to right order.

Specified by:
visitThrow in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitAssert

public R visitAssert(AssertTree node,
                     P p)

Visits an AssertTree node. This implementation scans the children in left to right order.

Specified by:
visitAssert in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitMethodInvocation

public R visitMethodInvocation(MethodInvocationTree node,
                               P p)

Visits a MethodInvocationTree node. This implementation scans the children in left to right order.

Specified by:
visitMethodInvocation in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitNewClass

public R visitNewClass(NewClassTree node,
                       P p)

Visits a NewClassTree node. This implementation scans the children in left to right order.

Specified by:
visitNewClass in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitNewArray

public R visitNewArray(NewArrayTree node,
                       P p)

Visits a NewArrayTree node. This implementation scans the children in left to right order.

Specified by:
visitNewArray in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitLambdaExpression

public R visitLambdaExpression(LambdaExpressionTree node,
                               P p)

Visits a LambdaExpressionTree node. This implementation scans the children in left to right order.

Specified by:
visitLambdaExpression in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitParenthesized

public R visitParenthesized(ParenthesizedTree node,
                            P p)

Visits a ParenthesizedTree node. This implementation scans the children in left to right order.

Specified by:
visitParenthesized in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitAssignment

public R visitAssignment(AssignmentTree node,
                         P p)

Visits an AssignmentTree node. This implementation scans the children in left to right order.

Specified by:
visitAssignment in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitCompoundAssignment

public R visitCompoundAssignment(CompoundAssignmentTree node,
                                 P p)

Visits a CompoundAssignmentTree node. This implementation scans the children in left to right order.

Specified by:
visitCompoundAssignment in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitUnary

public R visitUnary(UnaryTree node,
                    P p)

Visits a UnaryTree node. This implementation scans the children in left to right order.

Specified by:
visitUnary in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitBinary

public R visitBinary(BinaryTree node,
                     P p)

Visits a BinaryTree node. This implementation scans the children in left to right order.

Specified by:
visitBinary in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitTypeCast

public R visitTypeCast(TypeCastTree node,
                       P p)

Visits a TypeCastTree node. This implementation scans the children in left to right order.

Specified by:
visitTypeCast in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitInstanceOf

public R visitInstanceOf(InstanceOfTree node,
                         P p)

Visits an InstanceOfTree node. This implementation scans the children in left to right order.

Specified by:
visitInstanceOf in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitArrayAccess

public R visitArrayAccess(ArrayAccessTree node,
                          P p)

Visits an ArrayAccessTree node. This implementation scans the children in left to right order.

Specified by:
visitArrayAccess in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitMemberSelect

public R visitMemberSelect(MemberSelectTree node,
                           P p)

Visits a MemberSelectTree node. This implementation scans the children in left to right order.

Specified by:
visitMemberSelect in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitMemberReference

public R visitMemberReference(MemberReferenceTree node,
                              P p)

Visits a MemberReferenceTree node. This implementation scans the children in left to right order.

Specified by:
visitMemberReference in interface TreeVisitor<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 TreeVisitor<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 a LiteralTree node. This implementation returns null.

Specified by:
visitLiteral in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitPrimitiveType

public R visitPrimitiveType(PrimitiveTypeTree node,
                            P p)

Visits a PrimitiveTypeTree node. This implementation returns null.

Specified by:
visitPrimitiveType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitArrayType

public R visitArrayType(ArrayTypeTree node,
                        P p)

Visits an ArrayTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitArrayType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitParameterizedType

public R visitParameterizedType(ParameterizedTypeTree node,
                                P p)

Visits a ParameterizedTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitParameterizedType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitUnionType

public R visitUnionType(UnionTypeTree node,
                        P p)

Visits a UnionTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitUnionType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitIntersectionType

public R visitIntersectionType(IntersectionTypeTree node,
                               P p)

Visits an IntersectionTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitIntersectionType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitTypeParameter

public R visitTypeParameter(TypeParameterTree node,
                            P p)

Visits a TypeParameterTree node. This implementation scans the children in left to right order.

Specified by:
visitTypeParameter in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitWildcard

public R visitWildcard(WildcardTree node,
                       P p)

Visits a WildcardTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitWildcard in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitModifiers

public R visitModifiers(ModifiersTree node,
                        P p)

Visits a ModifiersTree node. This implementation scans the children in left to right order.

Specified by:
visitModifiers in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitAnnotation

public R visitAnnotation(AnnotationTree node,
                         P p)

Visits an AnnotatedTree node. This implementation scans the children in left to right order.

Specified by:
visitAnnotation in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitAnnotatedType

public R visitAnnotatedType(AnnotatedTypeTree node,
                            P p)

Visits an AnnotatedTypeTree node. This implementation scans the children in left to right order.

Specified by:
visitAnnotatedType in interface TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

visitOther

public R visitOther(Tree node,
                    P p)

Visits an unknown type of Tree node. This can occur if the language evolves and new kinds of nodes are added to the Tree hierarchy. This implementation returns null.

Specified by:
visitOther in interface TreeVisitor<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 TreeVisitor<R,​P>
Parameters:
node - the node being visited
p - a parameter value
Returns:
the result of scanning

© 1993, 2020, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/11/docs/api/jdk.compiler/com/sun/source/util/TreeScanner.html