FileLock Class
Definition
Important
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A token representing a lock on a region of a file.
[Android.Runtime.Register("java/nio/channels/FileLock", DoNotGenerateAcw=true)]
public abstract class FileLock : Java.Lang.Object, IDisposable, Java.Interop.IJavaPeerable, Java.Lang.IAutoCloseable[<Android.Runtime.Register("java/nio/channels/FileLock", DoNotGenerateAcw=true)>]
type FileLock = class
inherit Object
interface IAutoCloseable
interface IJavaObject
interface IDisposable
interface IJavaPeerable- Inheritance
- Attributes
- Implements
Remarks
A token representing a lock on a region of a file.
A file-lock object is created each time a lock is acquired on a file via one of the FileChannel#lock(long,long,boolean) lock or FileChannel#tryLock(long,long,boolean) tryLock methods of the FileChannel class, or the AsynchronousFileChannel#lock(long,long,boolean,Object,CompletionHandler) lock or AsynchronousFileChannel#tryLock(long,long,boolean) tryLock methods of the AsynchronousFileChannel class.
A file-lock object is initially valid. It remains valid until the lock is released by invoking the #release release method, by closing the channel that was used to acquire it, or by the termination of the Java virtual machine, whichever comes first. The validity of a lock may be tested by invoking its #isValid isValid method.
A file lock is either exclusive or shared. A shared lock prevents other concurrently-running programs from acquiring an overlapping exclusive lock, but does allow them to acquire overlapping shared locks. An exclusive lock prevents other programs from acquiring an overlapping lock of either type. Once it is released, a lock has no further effect on the locks that may be acquired by other programs.
Whether a lock is exclusive or shared may be determined by invoking its #isShared isShared method. Some platforms do not support shared locks, in which case a request for a shared lock is automatically converted into a request for an exclusive lock.
The locks held on a particular file by a single Java virtual machine do not overlap. The #overlaps overlaps method may be used to test whether a candidate lock range overlaps an existing lock.
A file-lock object records the file channel upon whose file the lock is held, the type and validity of the lock, and the position and size of the locked region. Only the validity of a lock is subject to change over time; all other aspects of a lock's state are immutable.
File locks are held on behalf of the entire Java virtual machine. They are not suitable for controlling access to a file by multiple threads within the same virtual machine.
File-lock objects are safe for use by multiple concurrent threads.
"pdep"><h2> Platform dependencies </h2>
This file-locking API is intended to map directly to the native locking facility of the underlying operating system. Thus the locks held on a file should be visible to all programs that have access to the file, regardless of the language in which those programs are written.
Whether or not a lock actually prevents another program from accessing the content of the locked region is system-dependent and therefore unspecified. The native file-locking facilities of some systems are merely advisory, meaning that programs must cooperatively observe a known locking protocol in order to guarantee data integrity. On other systems native file locks are mandatory, meaning that if one program locks a region of a file then other programs are actually prevented from accessing that region in a way that would violate the lock. On yet other systems, whether native file locks are advisory or mandatory is configurable on a per-file basis. To ensure consistent and correct behavior across platforms, it is strongly recommended that the locks provided by this API be used as if they were advisory locks.
On some systems, acquiring a mandatory lock on a region of a file prevents that region from being java.nio.channels.FileChannel#map <i>mapped into memory</i>, and vice versa. Programs that combine locking and mapping should be prepared for this combination to fail.
On some systems, closing a channel releases all locks held by the Java virtual machine on the underlying file regardless of whether the locks were acquired via that channel or via another channel open on the same file. It is strongly recommended that, within a program, a unique channel be used to acquire all locks on any given file.
Some network filesystems permit file locking to be used with memory-mapped files only when the locked regions are page-aligned and a whole multiple of the underlying hardware's page size. Some network filesystems do not implement file locks on regions that extend past a certain position, often 2<sup>30</sup> or 2<sup>31</sup>. In general, great care should be taken when locking files that reside on network filesystems.
Added in 1.4.
Java documentation for java.nio.channels.FileLock.
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
| FileLock(AsynchronousFileChannel, Int64, Int64, Boolean) |
Initializes a new instance of this class. |
| FileLock(FileChannel, Int64, Int64, Boolean) |
Initializes a new instance of this class. |
| FileLock(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) |
| IsShared |
Tells whether this lock is shared. |
| IsValid |
Indicates whether this lock is a valid file lock. |
| 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
| AcquiredBy() |
Returns the channel upon whose file this lock was acquired. |
| Channel() |
Returns the file channel upon whose file this lock was acquired. |
| Clone() |
Creates and returns a copy of this object. (Inherited from Object) |
| Close() |
This method invokes the |
| 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) |
| 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) |
| Overlaps(Int64, Int64) |
Tells whether or not this lock overlaps the given lock range. |
| Position() |
Returns the position within the file of the first byte of the locked region. |
| Release() |
Releases this lock. |
| SetHandle(IntPtr, JniHandleOwnership) |
Sets the Handle property. (Inherited from Object) |
| Size() |
Returns the size of the locked region in bytes. |
| ToArray<T>() | (Inherited from Object) |
| ToString() |
Returns a string describing the range, type, and validity of this lock. |
| 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) | |