Package org.eclipse.rdf4j.query.algebra

## Class ZeroLengthPath

- java.lang.Object
- - org.eclipse.rdf4j.query.algebra.AbstractQueryModelNode
  - - org.eclipse.rdf4j.query.algebra.ZeroLengthPath

- All Implemented Interfaces:
    `Serializable`, `Cloneable`, `GraphPatternGroupable`, `QueryModelNode`, `TupleExpr`, `VariableScopeChange`

      public class ZeroLengthPath
      extends AbstractQueryModelNode
      implements TupleExpr

  A tuple expression that matches a path of length zero against an RDF graph. They can can be targeted at one of three context scopes: all contexts, null context only, or named contexts only.
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `ZeroLengthPath()` |
    `ZeroLengthPath​(StatementPattern.Scope scope, Var subject, Var object)` | Creates a zero-length path that matches a subject-, predicate- and object variable against statements from the specified context scope.
    `ZeroLengthPath​(StatementPattern.Scope scope, Var subjVar, Var objVar, Var conVar)` | Creates a zero-length path that matches a subject-, predicate-, object- and context variable against statements from the specified context scope.
    `ZeroLengthPath​(Var subject, Var object)` | Creates a zero-length path that matches a subject-, predicate- and object variable against statements from all contexts.
    `ZeroLengthPath​(Var subject, Var object, Var context)` | Creates a zero-length path that matches a subject-, predicate-, object- and context variable against statements from all contexts.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `ZeroLengthPath` | `clone()` | Returns a (deep) clone of this query model node.
    `boolean` | `equals​(Object other)` | Returns true if this query model node and its children are recursively equal to o and its children.
    `Set<String>` | `getAssuredBindingNames()` | Gets the names of the bindings that are guaranteed to be present in the results produced by this tuple expression.
    `Set<String>` | `getBindingNames()` | Gets the names of the bindings that are, or can be, returned by this tuple expression when it is evaluated.
    `Var` | `getContextVar()` | Returns the context variable, if available.
    `Var` | `getObjectVar()` |
    `StatementPattern.Scope` | `getScope()` | Gets the context scope for the zero-length path.
    `String` | `getSignature()` | Default implementation of `QueryModelNode.getSignature()` that prints the name of the node's class.
    `Var` | `getSubjectVar()` |
    `List<Var>` | `getVarList()` |
    `<L extends Collection<Var>> L` | `getVars​(L varCollection)` | Adds the variables of this statement pattern to the supplied collection.
    `int` | `hashCode()` |
    `void` | `replaceChildNode​(QueryModelNode current, QueryModelNode replacement)` | Default implementation of `QueryModelNode.replaceChildNode(QueryModelNode, QueryModelNode)` that throws an `IllegalArgumentException` indicating that current is not a child node of this node.
    `void` | `setContextVar​(Var context)` |
    `void` | `setObjectVar​(Var object)` |
    `void` | `setScope​(StatementPattern.Scope scope)` | Sets the context scope for the zero-length path
    `void` | `setSubjectVar​(Var subject)` |
    `<X extends Exception> void` | `visit​(QueryModelVisitor<X> visitor)` | Visits this node.
    `<X extends Exception> void` | `visitChildren​(QueryModelVisitor<X> visitor)` | Dummy implementation of `QueryModelNode.visitChildren(org.eclipse.rdf4j.query.algebra.QueryModelVisitor<X>)` that does nothing.

    - ### Methods inherited from class org.eclipse.rdf4j.query.algebra.AbstractQueryModelNode

      `getCostEstimate, getParentNode, getResultSizeActual, getResultSizeEstimate, getTotalTimeNanosActual, isGraphPatternGroup, isVariableScopeChange, nullEquals, replaceNodeInList, replaceWith, setCostEstimate, setGraphPatternGroup, setParentNode, setResultSizeActual, setResultSizeEstimate, setTotalTimeNanosActual, setVariableScopeChange, toString`

    - ### Methods inherited from class java.lang.Object

      `finalize, getClass, notify, notifyAll, wait, wait, wait`

    - ### Methods inherited from interface org.eclipse.rdf4j.query.algebra.QueryModelNode

      `getCostEstimate, getParentNode, getResultSizeActual, getResultSizeEstimate, getTotalTimeNanosActual, replaceWith, setCostEstimate, setParentNode, setResultSizeActual, setResultSizeEstimate, setTotalTimeNanosActual, toString`

- - ### Constructor Detail

    - #### ZeroLengthPath

          public ZeroLengthPath()

    - #### ZeroLengthPath

          public ZeroLengthPath​(Var subject,
                                Var object)

      Creates a zero-length path that matches a subject-, predicate- and object variable against statements from all contexts.

    - #### ZeroLengthPath

          public ZeroLengthPath​(StatementPattern.Scope scope,
                                Var subject,
                                Var object)

      Creates a zero-length path that matches a subject-, predicate- and object variable against statements from the specified context scope.

    - #### ZeroLengthPath

          public ZeroLengthPath​(Var subject,
                                Var object,
                                Var context)

      Creates a zero-length path that matches a subject-, predicate-, object- and context variable against statements from all contexts.

    - #### ZeroLengthPath

          public ZeroLengthPath​(StatementPattern.Scope scope,
                                Var subjVar,
                                Var objVar,
                                Var conVar)

      Creates a zero-length path that matches a subject-, predicate-, object- and context variable against statements from the specified context scope.

  - ### Method Detail

    - #### getScope

          public StatementPattern.Scope getScope()

      Gets the context scope for the zero-length path.

    - #### setScope

          public void setScope​(StatementPattern.Scope scope)

      Sets the context scope for the zero-length path

    - #### getSubjectVar

          public Var getSubjectVar()

    - #### setSubjectVar

          public void setSubjectVar​(Var subject)

    - #### getObjectVar

          public Var getObjectVar()

    - #### setObjectVar

          public void setObjectVar​(Var object)

    - #### getContextVar

          public Var getContextVar()

      Returns the context variable, if available.

    - #### setContextVar

          public void setContextVar​(Var context)

    - #### getBindingNames

          public Set<String> getBindingNames()

      Description copied from interface: `TupleExpr`
      Gets the names of the bindings that are, or can be, returned by this tuple expression when it is evaluated.
      Specified by:
        `getBindingNames` in interface `TupleExpr`
      Returns:
        A set of binding names.

    - #### getAssuredBindingNames

          public Set<String> getAssuredBindingNames()

      Description copied from interface: `TupleExpr`
      Gets the names of the bindings that are guaranteed to be present in the results produced by this tuple expression.
      Specified by:
        `getAssuredBindingNames` in interface `TupleExpr`
      Returns:
        A set of binding names.

    - #### getVarList

          public List<Var> getVarList()

    - #### getVars

          public <L extends Collection<Var>> L getVars​(L varCollection)

      Adds the variables of this statement pattern to the supplied collection.

    - #### visit

          public <X extends Exception> void visit​(QueryModelVisitor<X> visitor)
                                           throws X extends Exception

      Description copied from interface: `QueryModelNode`
      Visits this node. The node reports itself to the visitor with the proper runtime type.
      Specified by:
        `visit` in interface `QueryModelNode`
      Throws:
        `X extends Exception`

    - #### visitChildren

          public <X extends Exception> void visitChildren​(QueryModelVisitor<X> visitor)
                                                   throws X extends Exception

      Description copied from class: `AbstractQueryModelNode`
      Dummy implementation of `QueryModelNode.visitChildren(org.eclipse.rdf4j.query.algebra.QueryModelVisitor<X>)` that does nothing. Subclasses should override this method when they have child nodes.
      Specified by:
        `visitChildren` in interface `QueryModelNode`
      Overrides:
        `visitChildren` in class `AbstractQueryModelNode`
      Throws:
        `X extends Exception`

    - #### replaceChildNode

          public void replaceChildNode​(QueryModelNode current,
                                       QueryModelNode replacement)

      Description copied from class: `AbstractQueryModelNode`
      Default implementation of `QueryModelNode.replaceChildNode(QueryModelNode, QueryModelNode)` that throws an `IllegalArgumentException` indicating that current is not a child node of this node.
      Specified by:
        `replaceChildNode` in interface `QueryModelNode`
      Overrides:
        `replaceChildNode` in class `AbstractQueryModelNode`
      Parameters:
        `current` - The current child node.
        `replacement` - The new child node.

    - #### getSignature

          public String getSignature()

      Description copied from class: `AbstractQueryModelNode`
      Default implementation of `QueryModelNode.getSignature()` that prints the name of the node's class.
      Specified by:
        `getSignature` in interface `QueryModelNode`
      Overrides:
        `getSignature` in class `AbstractQueryModelNode`
      Returns:
        The node's signature, e.g. SLICE (offset=10, limit=10).

    - #### equals

          public boolean equals​(Object other)

      Description copied from interface: `QueryModelNode`
      Returns true if this query model node and its children are recursively equal to o and its children.
      Specified by:
        `equals` in interface `QueryModelNode`
      Overrides:
        `equals` in class `Object`

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `Object`

    - #### clone

          public ZeroLengthPath clone()

      Description copied from interface: `QueryModelNode`
      Returns a (deep) clone of this query model node. This method recursively clones the entire node tree, starting from this nodes.
      Specified by:
        `clone` in interface `QueryModelNode`
      Specified by:
        `clone` in interface `TupleExpr`
      Overrides:
        `clone` in class `AbstractQueryModelNode`
      Returns:
        A deep clone of this query model node.