/*******************************************************************************
* Companion code for the book "Introduction to Software Design with Java",
* 2nd edition by Martin P. Robillard.
*
* Copyright (C) 2022 by Martin P. Robillard
*
* This code is licensed under a Creative Commons
* Attribution-NonCommercial-NoDerivatives 4.0 International License.
*
* See http://creativecommons.org/licenses/by-nc-nd/4.0/
*
*******************************************************************************/
package e2.chapter6;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* A CardSource implementation that represents an aggregation
* of zero or more card sources.
*/
public class CompositeCardSource implements CardSource
{
List<CardSource> aElements;
/**
* Creates a composite card source comprising all the elements
* in pCardSources
*
* @param pCardSources A sequence of cards sources to aggregate.
*/
public CompositeCardSource( pCardSources)
{
aElements = Arrays.;
}
@Override
public Card draw()
{
assert !isEmpty();
for( CardSource source : aElements )
{
if( !source.isEmpty() )
{
return source.draw();
}
}
;
return null;
}
@Override
public boolean isEmpty()
{
for( CardSource source : aElements )
{
if( !source.isEmpty() )
{
return false;
}
}
return true;
}
@Override
public CardSource copy() {
CompositeCardSource copy = new CompositeCardSource();
copy.aElements = new ArrayList<>();
for( CardSource source : aElements ) {
copy.aElements.add(source.copy());
}
return copy;
}
}The methods in this class all throw a NullPointerException,
if the specified array reference is null, except where noted.
The documentation for the methods contained in this class includes
brief descriptions of the implementations. Such descriptions should
be regarded as implementation notes, rather than parts of the
specification. Implementors should feel free to substitute other
algorithms, so long as the specification itself is adhered to. (For
example, the algorithm used by sort(Object[]) does not have to be
a MergeSort, but it does have to be stable.)
This class is a member of the Java Collections Framework.
This is a form of documentation, confirming that given the precondition, the loop is expected to find a non-empty source and to return out of the method from that point.
This is a form of documentation, confirming that given the precondition, the loop is expected to find a non-empty source and to return out of the method from that point.
The field is not declared final to allow cloning, as done
in method clone(). Otherwise, it would be better to declare this
field final.
The field is not declared final to allow cloning, as done
in method clone(). Otherwise, it would be better to declare this
field final.
This is an example of a vararg (variable arguments).
This is an example of a vararg (variable arguments).
Lists that support this operation may place limitations on what elements may be added to this list. In particular, some lists will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. List classes should clearly specify in their documentation any restrictions on what elements may be added.
add in interface Collection<E>e - element to be appended to this listtrue (as specified by Collection.add(E))UnsupportedOperationException - if the add operation
is not supported by this listClassCastException - if the class of the specified element
prevents it from being added to this listNullPointerException - if the specified element is null and this
list does not permit null elementsIllegalArgumentException - if some property of this element
prevents it from being added to this list
Unlike sets, lists typically allow duplicate elements. More formally,
lists typically allow pairs of elements e1 and e2
such that e1.equals(e2), and they typically allow multiple
null elements if they allow null elements at all. It is not inconceivable
that someone might wish to implement a list that prohibits duplicates, by
throwing runtime exceptions when the user attempts to insert them, but we
expect this usage to be rare.
The List interface places additional stipulations, beyond those
specified in the Collection interface, on the contracts of the
iterator, add, remove, equals, and
hashCode methods. Declarations for other inherited methods are
also included here for convenience.
The List interface provides four methods for positional (indexed)
access to list elements. Lists (like Java arrays) are zero based. Note
that these operations may execute in time proportional to the index value
for some implementations (the LinkedList class, for
example). Thus, iterating over the elements in a list is typically
preferable to indexing through it if the caller does not know the
implementation.
The List interface provides a special iterator, called a
ListIterator, that allows element insertion and replacement, and
bidirectional access in addition to the normal operations that the
Iterator interface provides. A method is provided to obtain a
list iterator that starts at a specified position in the list.
The List interface provides two methods to search for a specified
object. From a performance standpoint, these methods should be used with
caution. In many implementations they will perform costly linear
searches.
The List interface provides two methods to efficiently insert and
remove multiple elements at an arbitrary point in the list.
Note: While it is permissible for lists to contain themselves as elements,
extreme caution is advised: the equals and hashCode
methods are no longer well defined on such a list.
Some list implementations have restrictions on the elements that
they may contain. For example, some implementations prohibit null elements,
and some have restrictions on the types of their elements. Attempting to
add an ineligible element throws an unchecked exception, typically
NullPointerException or ClassCastException. Attempting
to query the presence of an ineligible element may throw an exception,
or it may simply return false; some implementations will exhibit the former
behavior and some will exhibit the latter. More generally, attempting an
operation on an ineligible element whose completion would not result in
the insertion of an ineligible element into the list may throw an
exception or it may succeed, at the option of the implementation.
Such exceptions are marked as "optional" in the specification for this
interface.
The List.of and
List.copyOf static factory methods
provide a convenient way to create unmodifiable lists. The List
instances created by these methods have the following characteristics:
UnsupportedOperationException to be thrown.
However, if the contained elements are themselves mutable,
this may cause the List's contents to appear to change.
null elements. Attempts to create them with
null elements result in NullPointerException.
subList views implement the
RandomAccess interface.
This interface is a member of the Java Collections Framework.
Varargs get converted to an array, which can then
easily be converted to a list using asList.
Serializable and implements RandomAccess.
Varargs get converted to an array, which can then
easily be converted to a list using asList.
Serializable and implements RandomAccess.
The returned list implements the optional Collection methods, except
those that would change the size of the returned list. Those methods leave
the list unchanged and throw UnsupportedOperationException.
Collection.toArray().
This method provides a way to wrap an existing array:
Integer[] numbers = ...
...
List<Integer> values = Arrays.asList(numbers);
This method also provides a convenient way to create a fixed-size list initialized to contain several elements:
List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");
The list returned by this method is modifiable.
To create an unmodifiable list, use
Collections.unmodifiableList
or Unmodifiable Lists.
T - the class of the objects in the arraya - the array by which the list will be backedNullPointerException - if the specified array is nullChapter 6, insight #3
Use the Composite when you need to manipulate collections of objects the same way as single leaf objects
Chapter 6, insight #3
Use the Composite when you need to manipulate collections of objects the same way as single leaf objects
List interface. Implements
all optional list operations, and permits all elements, including
null. In addition to implementing the List interface,
this class provides methods to manipulate the size of the array that is
used internally to store the list. (This class is roughly equivalent to
Vector, except that it is unsynchronized.)
List interface. Implements
all optional list operations, and permits all elements, including
null. In addition to implementing the List interface,
this class provides methods to manipulate the size of the array that is
used internally to store the list. (This class is roughly equivalent to
Vector, except that it is unsynchronized.)
The size, isEmpty, get, set,
iterator, and listIterator operations run in constant
time. The add operation runs in amortized constant time,
that is, adding n elements requires O(n) time. All of the other operations
run in linear time (roughly speaking). The constant factor is low compared
to that for the LinkedList implementation.
Each ArrayList instance has a capacity. The capacity is
the size of the array used to store the elements in the list. It is always
at least as large as the list size. As elements are added to an ArrayList,
its capacity grows automatically. The details of the growth policy are not
specified beyond the fact that adding an element has constant amortized
time cost.
An application can increase the capacity of an ArrayList instance
before adding a large number of elements using the ensureCapacity
operation. This may reduce the amount of incremental reallocation.
Note that this implementation is not synchronized.
If multiple threads access an ArrayList instance concurrently,
and at least one of the threads modifies the list structurally, it
must be synchronized externally. (A structural modification is
any operation that adds or deletes one or more elements, or explicitly
resizes the backing array; merely setting the value of an element is not
a structural modification.) This is typically accomplished by
synchronizing on some object that naturally encapsulates the list.
If no such object exists, the list should be "wrapped" using the
Collections.synchronizedList
method. This is best done at creation time, to prevent accidental
unsynchronized access to the list:
List list = Collections.synchronizedList(new ArrayList(...));
The iterators returned by this class's iterator and
listIterator methods are fail-fast:
if the list is structurally modified at any time after the iterator is
created, in any way except through the iterator's own
remove or
add methods, the iterator will throw a
ConcurrentModificationException. Thus, in the face of
concurrent modification, the iterator fails quickly and cleanly, rather
than risking arbitrary, non-deterministic behavior at an undetermined
time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed
as it is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators
throw ConcurrentModificationException on a best-effort basis.
Therefore, it would be wrong to write a program that depended on this
exception for its correctness: the fail-fast behavior of iterators
should be used only to detect bugs.
This class is a member of the Java Collections Framework.