AbstractQueue
abstract class AbstractQueue<E : Any!> : AbstractCollection<E>, Queue<E>
This class provides skeletal implementations of some Queue operations. The implementations in this class are appropriate when the base implementation does not allow null elements. Methods add, remove, and element are based on offer, , and peek, respectively, but throw exceptions instead of indicating failure via false or null returns.
A Queue implementation that extends this class must minimally define a method Queue#offer which does not permit insertion of null elements, along with methods Queue#peek, Queue#poll, Collection#size, and Collection#iterator. Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassing AbstractCollection.
Summary
| Protected constructors |
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Constructor for use by subclasses.
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| Public methods |
| open Boolean |
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available.
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| open Boolean |
Adds all of the elements in the specified collection to this queue.
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| open Unit |
Removes all of the elements from this queue.
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| open E |
Retrieves, but does not remove, the head of this queue.
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| open E |
Retrieves and removes the head of this queue.
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| Inherited functions |
From class AbstractCollection
Boolean |
contains(element: E?)
Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that (o==null ? e==null : o.equals(e)).
This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
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Boolean |
containsAll(elements: Collection<E>)
Returns true if this collection contains all of the elements in the specified collection.
This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection. If all elements are so contained true is returned, otherwise false.
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Boolean |
isEmpty()
Returns true if this collection contains no elements.
This implementation returns size() == 0.
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MutableIterator<E> |
iterator()
Returns an iterator over the elements contained in this collection.
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Boolean |
remove(element: E?)
Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e such that (o==null ? e==null : o.equals(e)), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).
This implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.
Note that this implementation throws an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection contains the specified object.
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Boolean |
removeAll(elements: Collection<E>)
Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.
This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's so contained, it's removed from this collection with the iterator's remove method.
Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements in common with the specified collection.
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Boolean |
retainAll(elements: Collection<E>)
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's not so contained, it's removed from this collection with the iterator's remove method.
Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements not present in the specified collection.
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Array<Any!> |
toArray()
Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index 0. The length of the returned array is equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The size method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.
This method is equivalent to:
<code>List<E> list = new ArrayList<E>(size());
for (E e : this)
list.add(e);
return list.toArray();
</code>
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Array<T> |
toArray(a: Array<T>)
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this collection.
If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain any null elements.)
If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.
Suppose x is a collection known to contain only strings. The following code can be used to dump the collection into a newly allocated array of String:
String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0]) is identical in function to toArray().
This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index 0. If the number of elements returned by the iterator is too large to fit into the specified array, then the elements are returned in a newly allocated array with length equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The size method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.
This method is equivalent to:
<code>List<E> list = new ArrayList<E>(size());
for (E e : this)
list.add(e);
return list.toArray(a);
</code>
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String |
toString()
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String#valueOf(Object).
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From class Queue
Boolean |
offer(e: E)
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions. When using a capacity-restricted queue, this method is generally preferable to add, which can fail to insert an element only by throwing an exception.
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E? |
peek()
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
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E? |
poll()
Retrieves and removes the head of this queue, or returns null if this queue is empty.
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Protected constructors
<init>
protected AbstractQueue()
Constructor for use by subclasses.
Public methods
add
open fun add(element: E): Boolean
Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available.
This implementation returns true if offer succeeds, else throws an IllegalStateException.
| Parameters |
e |
the element to add |
| Exceptions |
java.lang.UnsupportedOperationException |
if the add operation is not supported by this collection |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this queue |
java.lang.NullPointerException |
if the specified element is null and this queue does not permit null elements |
java.lang.IllegalArgumentException |
if some property of this element prevents it from being added to this queue |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
addAll
open fun addAll(elements: Collection<E>): Boolean
Adds all of the elements in the specified collection to this queue. Attempts to addAll of a queue to itself result in IllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.
This implementation iterates over the specified collection, and adds each element returned by the iterator to this queue, in turn. A runtime exception encountered while trying to add an element (including, in particular, a null element) may result in only some of the elements having been successfully added when the associated exception is thrown.
| Parameters |
c |
collection containing elements to be added to this queue |
| Return |
Boolean |
true if this queue changed as a result of the call |
| Exceptions |
java.lang.UnsupportedOperationException |
if the addAll operation is not supported by this collection |
java.lang.ClassCastException |
if the class of an element of the specified collection prevents it from being added to this queue |
java.lang.NullPointerException |
if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null |
java.lang.IllegalArgumentException |
if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queue |
java.lang.IllegalStateException |
if not all the elements can be added at this time due to insertion restrictions |
clear
open fun clear(): Unit
Removes all of the elements from this queue. The queue will be empty after this call returns.
This implementation repeatedly invokes poll until it returns null.
| Exceptions |
java.lang.UnsupportedOperationException |
if the clear operation is not supported by this collection |
element
open fun element(): E
Retrieves, but does not remove, the head of this queue. This method differs from peek only in that it throws an exception if this queue is empty.
This implementation returns the result of peek unless the queue is empty.
| Return |
E |
the head of this queue |
| Exceptions |
java.util.NoSuchElementException |
if this queue is empty |
remove
open fun remove(): E
Retrieves and removes the head of this queue. This method differs from poll only in that it throws an exception if this queue is empty.
This implementation returns the result of poll unless the queue is empty.
| Return |
E |
the head of this queue |
| Exceptions |
java.util.NoSuchElementException |
if this queue is empty |
