TypeVisitor (Evaluating Software Design Patterns - Master's Thesis by Gunni Rode)

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Evaluating Software Design Patterns
— the "Gang of Four" patterns implemented in Java 6

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dk.rode.thesis.visitor
Class TypeVisitor

java.lang.Object
  dk.rode.thesis.visitor.TypeVisitor

All Implemented Interfaces:: SequenceTypeVisitor<Void>, SequenceVisitor<Void>

@Participant(value="ConcreteVisitor") public class TypeVisitor
extends Object
implements SequenceTypeVisitor<Void>
extends Object
implements SequenceTypeVisitor<Void>

A type visitor collects visited sequences based on acceptance of specific sequence types.

It handles only type visitable sequences.

The collected types correspond to the visitation methods overridden by sub-classes of this visitor. If this visitor is used as is, it will accept no sequence types: each visitation method does nothing per default. A sub-class must simply invoke approve(Sequence) to signal that a given visited sequence is approved.

The visitor accumulates the visited sequences in visitation order. They can be collected after visitation via the getApproved() method. A given sequence is only included once in the returned list, based on equals, not identity.

Author:: Gunni Rode / rode.dk
See Also:: LoggingVisitor, CountingVisitor, SimpleScanner

Field Summary
`private Set<Sequence<?>>`	`approved` The set containing the approved sequences, in order.

Constructor Summary
`TypeVisitor()` No-arg constructor.

Method Summary
`protected void`	`approve(Sequence<?> sequence)` Approves the visited sequence supplied as `sequence`.
`int`	`approved()` Returns the number of sequences approved by this visitor.
`void`	`clear()` Clears the accumulated approved sequences, so this visitor can be reused.
`List<Sequence<?>>`	`getApproved()` Returns a list containing the sequences approved by this type visitor, in visitation order.
`String`	`toString()` Returns the string representation of this visitor.
`void`	`visitComposite(CompositeSequence<?> sequence, Void unused)` Visits a `composite` sequence.
`void`	`visitMemorizable(MemorizableSequence<?> sequence, Void unused)` Visits a `memorizable` sequence.
`void`	`visitObservable(ObservableSequence<?,?,?> sequence, Void unused)` Visits an `observable` sequence.
`void`	`visitReversible(ReversibleSequence<?> sequence, Void unused)` Visits a `reversible` sequence.
`void`	`visitStateable(StateableSequence<?> sequence, Void unused)` Visits a `stateable` sequence.
`void`	`visitUnknown(Sequence<?> sequence, Void unused)` Visits a `sequence` that cannot be visited by any other visitation methods declared by this visitor.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

approved

private final Set<Sequence<?>> approved

The set containing the approved sequences, in order.

Never null, but may be empty.

Constructor Detail

TypeVisitor

public TypeVisitor()

No-arg constructor.

Method Detail

approve

protected void approve(Sequence<?> sequence)

Approves the visited sequence supplied as sequence.

Parameters:: sequence - The sequence to approve; cannot be null.
Throws:: NullPointerException - if sequence is null.

approved

public int approved()

Returns the number of sequences approved by this visitor.

Returns:: The number of sequences approved.
See Also:: getApproved()

clear

public void clear()

Clears the accumulated approved sequences, so this visitor can be reused.

getApproved

public List<Sequence<?>> getApproved()

Returns a list containing the sequences approved by this type visitor, in visitation order.

Modifying the returned list will not affect this visitor.

Returns:: The list of sequences approved; never null, but can be empty.

toString

public String toString()

Returns the string representation of this visitor.

Overrides:: toString in class Object

Returns:: The string representation; never null.