/**
* Copyright (C) 2022 by Martin Robillard. See https://codesample.info/about.html
*/
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 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).
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.
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.
If the specified array's actual component type differs from the type
parameter T, this can result in operations on the returned list throwing an
ArrayStoreException.
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 nullList 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.
Chapter 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
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.
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.
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 list
true (as specified by Collection.add(E))
UnsupportedOperationException - if the add operation is not supported by this list
ClassCastException - if the class of the specified element prevents it from being added to this list
NullPointerException - if the specified element is null and this list does not permit null elements
IllegalArgumentException - if some property of this element prevents it from being added to this list