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

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

    • Constructor Detail

      • TreeScanner

        public TreeScanner()

    • Method Detail

      • 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