dk.rode.thesis.decorator
Class SequenceDecorator<E>

java.lang.Object
  dk.rode.thesis.decorator.SequenceDecorator<E>

Type Parameters:

E - The type of values delivered by this sequence.

All Implemented Interfaces:

Sequence<E>, Copyable<Sequence<E>>, StrictCopyable<Sequence<E>>, Stringable<Sequence<E>>

Direct Known Subclasses:

AbstractVisitableSequence, AppenderDecorator, DuplexDecorator, IterableSequence, NonResettableSequence, ProcessableSequence, SynchronisedSequence, UppercaseDecorator

@ParticipantUsage(value={"Component","ConcreteComponent"},
                  type=Sequence.class)
@Participant(value="Decorator")
public abstract class SequenceDecorator<E>
extends Object
implements Sequence<E>

A sequence decorator is a decorator that forwards all request to the decorated Sequence without performing additional operations except for toString().

Sub-classes can override current() and next() to add functionality, but must implement Sequence.copy().

A sequence decorator exhibit the same bounded, consistent, and unique properties as the decorated sequence.

The default stringable policy used is DecoratedPolicy.VISIBLE.

Implementation notes:
The decorated sequence must have the exact same type parameter, E, and not <? extends E> is not allowed. To facilitate different type parameters, the Adapter pattern can be used.

Author:

Gunni Rode / rode.dk

Nested Class Summary

Nested classes/interfaces inherited from interface dk.rode.thesis.meta.model.Sequence

Sequence.State

Field Summary

private StringablePolicy<Sequence<?>>	policy The default sequence policy used for formatting.
(package private) Sequence<E>	sequence The decorated sequence.

Constructor Summary

protected	SequenceDecorator(Sequence<E> sequence) Constructor, which creates this decorator to decorate the Sequence supplied as sequence.
protected	SequenceDecorator(Sequence<E> sequence, StringablePolicy<Sequence<?>> policy) Constructor, which creates this decorator to decorate the Sequence supplied as sequence and use the default stringable policy supplied as policy.

Method Summary

boolean	bounded() Returns true if this sequence is bounded, i.e.
boolean	consistent() Returns true if this sequence is consistent, i.e. deliver the same values, in order, after restart or reset.
E	current() Returns the current element from this sequence.
boolean	equals(Object object)
protected Sequence<E>	getSequence(boolean copy) Returns a copy of the decorated sequence if copy is true, otherwise the decorated sequence it self.
StringablePolicy<? super Sequence<E>>	getStringablePolicy(StringablePolicy<? super Sequence<E>> policy) Always return a non-null policy: policy is not null: policy is returned.
int	hashCode()
E	next() Returns the next element from this sequence.
void	reset() Resets this sequence to start over if it is consistent.
Sequence.State	state() Returns the internal state of this sequence.
String	toString()
CharSequence	toString(StringablePolicy<? super Sequence<E>> policy) Returns a char sequence representation of this stringable object using the format determined by policy or the default policy in case policy is null.
boolean	unique() Returns true if this sequence deliver a given sequence value at most one time until reset or restarted.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface dk.rode.thesis.meta.model.Sequence

copy

Field Detail

policy

private final StringablePolicy<Sequence<?>> policy

The default sequence policy used for formatting.

Can be null, in which case the default policy of decorated sequence is used.

sequence

final Sequence<E> sequence

The decorated sequence.

Never null.

Constructor Detail

SequenceDecorator

protected SequenceDecorator(@Participant(value="Component")
                            Sequence<E> sequence)

Constructor, which creates this decorator to decorate the Sequence supplied as sequence.

The default stringable policy used is DecoratedPolicy.VISIBLE.

Parameters:

sequence - The sequence; cannot be null.

Throws:

NullPointerException - If sequence is null.

SequenceDecorator

protected SequenceDecorator(@Participant(value="Component")
                            Sequence<E> sequence,
                            StringablePolicy<Sequence<?>> policy)

Constructor, which creates this decorator to decorate the Sequence supplied as sequence and use the default stringable policy supplied as policy.

Parameters:

sequence - The sequence; cannot be null.

policy - The default policy; can be null.

Throws:

NullPointerException - If sequence is null.

Method Detail

bounded

public boolean bounded()

Description copied from interface: Sequence

Returns true if this sequence is bounded, i.e. deliver values between the initial sequence value and some upper bound.

The same type of sequence may represent both bounded and unbounded sequences and the behaviour is determined and fixed at construction time. Bounded sequences will restart if they deliver consistent values.

Specified by:

bounded in interface Sequence<E>

Returns:

True if bounded, false if not.

See Also:

Sequence.unique()

consistent

public boolean consistent()

Description copied from interface: Sequence

Returns true if this sequence is consistent, i.e. deliver the same values, in order, after restart or reset.

Only bounded consistent sequences will restart. Consistent sequences need not deliver unique sequence values.

Instances of the same type of sequences are always consistent or inconsistent; it is determined at design time, not construction time.

Specified by:

consistent in interface Sequence<E>

Returns:

True if consistent, false if not.

current

public E current()

Description copied from interface: Sequence

Returns the current element from this sequence.

This method can be invoked even if Sequence.next() has not been invoked yet, thus delivering the initial value of this sequence.

Specified by:

current in interface Sequence<E>

Returns:

The current element; never null.

equals

public boolean equals(Object object)

Overrides:

equals in class Object

getSequence

protected Sequence<E> getSequence(boolean copy)

Returns a copy of the decorated sequence if copy is true, otherwise the decorated sequence it self.

Parameters:

copy - True to return a copy of the decorated sequence, false to return a reference to the sequence.

Returns:

The decorated sequence, as a copy if copy is true; never null.

getStringablePolicy

public StringablePolicy<? super Sequence<E>> getStringablePolicy(StringablePolicy<? super Sequence<E>> policy)

Description copied from interface: Stringable

Always return a non-null policy:

1. policy is not null: policy is returned.

2. policy is null: a default, non-null policy is returned.

Specified by:

getStringablePolicy in interface Stringable<Sequence<E>>

Parameters:

policy - The supplied policy; can be null.

Returns:

The policy to use; never null.

See Also:

Stringable.toString(StringablePolicy)

hashCode

public int hashCode()

Overrides:

hashCode in class Object

next

public E next()

Description copied from interface: Sequence

Returns the next element from this sequence.

Specified by:

next in interface Sequence<E>

Returns:

The next element; never null.

See Also:

Sequence.current(), Sequence.state()

reset

public void reset()

Description copied from interface: Sequence

Resets this sequence to start over if it is consistent.

If this sequence is consistent, the sequence will restart.

Specified by:

reset in interface Sequence<E>

state

public Sequence.State state()

Description copied from interface: Sequence

Returns the internal state of this sequence.

Specified by:

state in interface Sequence<E>

Returns:

The internal state; never null.

toString

public String toString()

Overrides:

toString in class Object

toString

public CharSequence toString(StringablePolicy<? super Sequence<E>> policy)

Description copied from interface: Stringable

Returns a char sequence representation of this stringable object using the format determined by policy or the default policy in case policy is null.

In Foo, a typical implementation of this method could be:

    public CharSequence toString(StringablePolicy<? super Foo> policy) {
      return this.getStringablePolicy(policy).toString(this);
    }
 

There are two approaches to formatting this stringable object into a char sequence representation:

1. Let policy decide the entire format, as in the Foo example above; or

2. Use policy to format part of the overall representation, for example letting this method append certain text regardless of the policy used.

Bullet 1) is not always applicable because a given policy implementation may not have access to all required information in its StringablePolicy.toString(Object) method, for example in case multiple stringable objects should be formatted into an overall representation.

In case an implementation uses the approach from bullet 2), care must be take to respect the policy hints so the overall format remains meaningful.

Specified by:

toString in interface Stringable<Sequence<E>>

Parameters:

policy - The policy to dictate the formatting; can be null, in which case the result of toString method is returned.

Returns:

The char sequence representation; never null.

See Also:

StringablePolicy.Type

unique

public boolean unique()

Description copied from interface: Sequence

Returns true if this sequence deliver a given sequence value at most one time until reset or restarted.

Unbounded sequences that are unique will never deliver the same sequence value more than once.

The same type of sequence may represent both unique and not unique sequences and the behaviour is determined and fixed at construction time.

Specified by:

unique in interface Sequence<E>

Returns:

True if unique, false if not.

See Also:

Sequence.consistent()