HashSet Class
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
This class implements the Set interface, backed by a hash table
(actually a HashMap instance).
[Android.Runtime.Register("java/util/HashSet", DoNotGenerateAcw=true)]
[Java.Interop.JavaTypeParameters(new System.String[] { "E" })]
public class HashSet : Java.Util.AbstractSet, IDisposable, Java.Interop.IJavaPeerable, Java.IO.ISerializable, Java.Lang.ICloneable[<Android.Runtime.Register("java/util/HashSet", DoNotGenerateAcw=true)>]
[<Java.Interop.JavaTypeParameters(new System.String[] { "E" })>]
type HashSet = class
inherit AbstractSet
interface ISerializable
interface IJavaObject
interface IDisposable
interface IJavaPeerable
interface ICloneable
interface ISet
interface ICollection
interface IIterable- Inheritance
- Derived
- Attributes
- Implements
Remarks
This class implements the Set interface, backed by a hash table (actually a HashMap instance). It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. This class permits the null element.
This class offers constant time performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets. Iterating over this set requires time proportional to the sum of the HashSet instance's size (the number of elements) plus the "capacity" of the backing HashMap instance (the number of buckets). Thus, it's very important not to set the initial capacity too high (or the load factor too low) if iteration performance is important.
<strong>Note that this implementation is not synchronized.</strong> If multiple threads access a hash set concurrently, and at least one of the threads modifies the set, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the set.
If no such object exists, the set should be "wrapped" using the Collections#synchronizedSet Collections.synchronizedSet method. This is best done at creation time, to prevent accidental unsynchronized access to the set:
Set s = Collections.synchronizedSet(new HashSet(...));
The iterators returned by this class's iterator method are fail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's own remove method, the Iterator throws 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.
Added in 1.2.
Java documentation for java.util.HashSet.
Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.
Constructors
| HashSet() |
Constructs a new, empty set; the backing |
| HashSet(ICollection) |
Constructs a new set containing the elements in the specified collection. |
| HashSet(Int32, Single) |
Constructs a new, empty set; the backing |
| HashSet(Int32) |
Constructs a new, empty set; the backing |
| HashSet(IntPtr, JniHandleOwnership) |
A constructor used when creating managed representations of JNI objects; called by the runtime. |
Properties
| Class |
Returns the runtime class of this |
| Handle |
The handle to the underlying Android instance. (Inherited from Object) |
| IsEmpty |
To be added (Inherited from AbstractCollection) |
| JniIdentityHashCode | (Inherited from Object) |
| JniPeerMembers | |
| PeerReference | (Inherited from Object) |
| ThresholdClass |
This API supports the Mono for Android infrastructure and is not intended to be used directly from your code. |
| ThresholdType |
This API supports the Mono for Android infrastructure and is not intended to be used directly from your code. |
Methods
| Add(Object) |
To be added (Inherited from AbstractCollection) |
| AddAll(ICollection) |
To be added (Inherited from AbstractCollection) |
| Clear() |
To be added (Inherited from AbstractCollection) |
| Clone() |
Returns a shallow copy of this |
| Contains(Object) |
To be added (Inherited from AbstractCollection) |
| ContainsAll(ICollection) |
To be added (Inherited from AbstractCollection) |
| Dispose() | (Inherited from Object) |
| Dispose(Boolean) | (Inherited from Object) |
| Equals(Object) |
Indicates whether some other object is "equal to" this one. (Inherited from Object) |
| GetHashCode() |
Returns a hash code value for the object. (Inherited from Object) |
| Iterator() |
Returns an iterator over the elements in this set. |
| JavaFinalize() |
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. (Inherited from Object) |
| Notify() |
Wakes up a single thread that is waiting on this object's monitor. (Inherited from Object) |
| NotifyAll() |
Wakes up all threads that are waiting on this object's monitor. (Inherited from Object) |
| Remove(Object) |
To be added (Inherited from AbstractCollection) |
| RemoveAll(ICollection) |
To be added (Inherited from AbstractCollection) |
| RetainAll(ICollection) |
To be added (Inherited from AbstractCollection) |
| SetHandle(IntPtr, JniHandleOwnership) |
Sets the Handle property. (Inherited from Object) |
| Size() |
Returns the number of elements in this set (its cardinality). |
| Spliterator() |
Creates a <em>late-binding</em>
and <em>fail-fast</em> |
| ToArray() |
To be added (Inherited from AbstractCollection) |
| ToArray(Object[]) |
To be added (Inherited from AbstractCollection) |
| ToArray<T>() | (Inherited from Object) |
| ToString() |
Returns a string representation of the object. (Inherited from Object) |
| UnregisterFromRuntime() | (Inherited from Object) |
| Wait() |
Causes the current thread to wait until it is awakened, typically by being <em>notified</em> or <em>interrupted</em>. (Inherited from Object) |
| Wait(Int64, Int32) |
Causes the current thread to wait until it is awakened, typically by being <em>notified</em> or <em>interrupted</em>, or until a certain amount of real time has elapsed. (Inherited from Object) |
| Wait(Int64) |
Causes the current thread to wait until it is awakened, typically by being <em>notified</em> or <em>interrupted</em>, or until a certain amount of real time has elapsed. (Inherited from Object) |
Explicit Interface Implementations
| IJavaPeerable.Disposed() | (Inherited from Object) |
| IJavaPeerable.DisposeUnlessReferenced() | (Inherited from Object) |
| IJavaPeerable.Finalized() | (Inherited from Object) |
| IJavaPeerable.JniManagedPeerState | (Inherited from Object) |
| IJavaPeerable.SetJniIdentityHashCode(Int32) | (Inherited from Object) |
| IJavaPeerable.SetJniManagedPeerState(JniManagedPeerStates) | (Inherited from Object) |
| IJavaPeerable.SetPeerReference(JniObjectReference) | (Inherited from Object) |
Extension Methods
| JavaCast<TResult>(IJavaObject) |
Performs an Android runtime-checked type conversion. |
| JavaCast<TResult>(IJavaObject) | |
| GetJniTypeName(IJavaPeerable) | |
| ToEnumerable(IIterable) | |
| ToEnumerable<T>(IIterable) | |