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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package java.util.concurrent.locks; |
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|
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import java.util.Collection; |
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import java.util.concurrent.TimeUnit; |
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|
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/** |
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* A reentrant mutual exclusion {@link Lock} with the same basic |
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* behavior and semantics as the implicit monitor lock accessed using |
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* {@code synchronized} methods and statements, but with extended |
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* capabilities. |
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* |
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* <p>A {@code ReentrantLock} is <em>owned</em> by the thread last |
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* successfully locking, but not yet unlocking it. A thread invoking |
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* {@code lock} will return, successfully acquiring the lock, when |
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* the lock is not owned by another thread. The method will return |
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* immediately if the current thread already owns the lock. This can |
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* be checked using methods {@link #isHeldByCurrentThread}, and {@link |
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* #getHoldCount}. |
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* |
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* <p>The constructor for this class accepts an optional |
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* <em>fairness</em> parameter. When set {@code true}, under |
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* contention, locks favor granting access to the longest-waiting |
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* thread. Otherwise this lock does not guarantee any particular |
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* access order. Programs using fair locks accessed by many threads |
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* may display lower overall throughput (i.e., are slower; often much |
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* slower) than those using the default setting, but have smaller |
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* variances in times to obtain locks and guarantee lack of |
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* starvation. Note however, that fairness of locks does not guarantee |
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* fairness of thread scheduling. Thus, one of many threads using a |
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* fair lock may obtain it multiple times in succession while other |
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* active threads are not progressing and not currently holding the |
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* lock. |
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* Also note that the untimed {@link #tryLock()} method does not |
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* honor the fairness setting. It will succeed if the lock |
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* is available even if other threads are waiting. |
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* |
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* <p>It is recommended practice to <em>always</em> immediately |
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* follow a call to {@code lock} with a {@code try} block, most |
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* typically in a before/after construction such as: |
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* |
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* <pre> {@code |
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* class X { |
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* private final ReentrantLock lock = new ReentrantLock(); |
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* // ... |
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* |
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* public void m() { |
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* lock.lock(); // block until condition holds |
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* try { |
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* // ... method body |
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* } finally { |
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* lock.unlock() |
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* } |
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* } |
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* }}</pre> |
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* |
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* <p>In addition to implementing the {@link Lock} interface, this |
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* class defines a number of {@code public} and {@code protected} |
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* methods for inspecting the state of the lock. Some of these |
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* methods are only useful for instrumentation and monitoring. |
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* |
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* <p>Serialization of this class behaves in the same way as built-in |
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* locks: a deserialized lock is in the unlocked state, regardless of |
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* its state when serialized. |
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* |
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* <p>This lock supports a maximum of 2147483647 recursive locks by |
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* the same thread. Attempts to exceed this limit result in |
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* {@link Error} throws from locking methods. |
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* |
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* @since 1.5 |
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* @author Doug Lea |
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*/ |
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public class ReentrantLock implements Lock, java.io.Serializable { |
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private static final long serialVersionUID = 7373984872572414699L; |
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/** Synchronizer providing all implementation mechanics */ |
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private final Sync sync; |
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|
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/** |
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* Base of synchronization control for this lock. Subclassed |
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* into fair and nonfair versions below. Uses AQS state to |
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* represent the number of holds on the lock. |
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*/ |
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abstract static class Sync extends AbstractQueuedSynchronizer { |
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private static final long serialVersionUID = -5179523762034025860L; |
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|
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/** |
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* Performs {@link Lock#lock}. The main reason for subclassing |
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* is to allow fast path for nonfair version. |
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*/ |
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abstract void lock(); |
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|
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/** |
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* Performs non-fair tryLock. tryAcquire is implemented in |
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* subclasses, but both need nonfair try for trylock method. |
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*/ |
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final boolean nonfairTryAcquire(int acquires) { |
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final Thread current = Thread.currentThread(); |
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int c = getState(); |
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if (c == 0) { |
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if (compareAndSetState(0, acquires)) { |
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setExclusiveOwnerThread(current); |
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return true; |
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} |
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} |
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else if (current == getExclusiveOwnerThread()) { |
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int nextc = c + acquires; |
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if (nextc < 0) // overflow |
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throw new Error("Maximum lock count exceeded"); |
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setState(nextc); |
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return true; |
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} |
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return false; |
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} |
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|
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protected final boolean tryRelease(int releases) { |
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int c = getState() - releases; |
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if (Thread.currentThread() != getExclusiveOwnerThread()) |
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throw new IllegalMonitorStateException(); |
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boolean free = false; |
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if (c == 0) { |
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free = true; |
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setExclusiveOwnerThread(null); |
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} |
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setState(c); |
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return free; |
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} |
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|
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protected final boolean isHeldExclusively() { |
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// While we must in general read state before owner, |
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// we don't need to do so to check if current thread is owner |
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return getExclusiveOwnerThread() == Thread.currentThread(); |
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} |
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|
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final ConditionObject newCondition() { |
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return new ConditionObject(); |
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} |
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|
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// Methods relayed from outer class |
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|
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final Thread getOwner() { |
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return getState() == 0 ? null : getExclusiveOwnerThread(); |
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} |
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|
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final int getHoldCount() { |
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return isHeldExclusively() ? getState() : 0; |
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} |
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|
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final boolean isLocked() { |
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return getState() != 0; |
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} |
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|
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/** |
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* Reconstitutes the instance from a stream (that is, deserializes it). |
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*/ |
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private void readObject(java.io.ObjectInputStream s) |
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throws java.io.IOException, ClassNotFoundException { |
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s.defaultReadObject(); |
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setState(0); // reset to unlocked state |
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} |
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} |
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|
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/** |
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* Sync object for non-fair locks |
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*/ |
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static final class NonfairSync extends Sync { |
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private static final long serialVersionUID = 7316153563782823691L; |
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|
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/** |
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* Performs lock. Try immediate barge, backing up to normal |
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* acquire on failure. |
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*/ |
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final void lock() { |
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if (compareAndSetState(0, 1)) |
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setExclusiveOwnerThread(Thread.currentThread()); |
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else |
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acquire(1); |
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} |
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|
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protected final boolean tryAcquire(int acquires) { |
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return nonfairTryAcquire(acquires); |
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} |
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} |
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|
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/** |
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* Sync object for fair locks |
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*/ |
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static final class FairSync extends Sync { |
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private static final long serialVersionUID = -3000897897090466540L; |
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|
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final void lock() { |
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acquire(1); |
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} |
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|
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/** |
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* Fair version of tryAcquire. Don't grant access unless |
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* recursive call or no waiters or is first. |
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*/ |
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protected final boolean tryAcquire(int acquires) { |
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final Thread current = Thread.currentThread(); |
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int c = getState(); |
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if (c == 0) { |
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if (!hasQueuedPredecessors() && |
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compareAndSetState(0, acquires)) { |
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setExclusiveOwnerThread(current); |
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return true; |
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} |
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} |
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else if (current == getExclusiveOwnerThread()) { |
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int nextc = c + acquires; |
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if (nextc < 0) |
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throw new Error("Maximum lock count exceeded"); |
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setState(nextc); |
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return true; |
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} |
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return false; |
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} |
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} |
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|
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/** |
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* Creates an instance of {@code ReentrantLock}. |
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* This is equivalent to using {@code ReentrantLock(false)}. |
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*/ |
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public ReentrantLock() { |
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sync = new NonfairSync(); |
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} |
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|
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/** |
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* Creates an instance of {@code ReentrantLock} with the |
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* given fairness policy. |
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* |
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* @param fair {@code true} if this lock should use a fair ordering policy |
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*/ |
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public ReentrantLock(boolean fair) { |
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sync = fair ? new FairSync() : new NonfairSync(); |
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} |
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|
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/** |
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* Acquires the lock. |
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* |
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* <p>Acquires the lock if it is not held by another thread and returns |
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* immediately, setting the lock hold count to one. |
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* |
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* <p>If the current thread already holds the lock then the hold |
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* count is incremented by one and the method returns immediately. |
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* |
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* <p>If the lock is held by another thread then the |
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* current thread becomes disabled for thread scheduling |
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* purposes and lies dormant until the lock has been acquired, |
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* at which time the lock hold count is set to one. |
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*/ |
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public void lock() { |
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sync.lock(); |
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} |
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|
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/** |
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* Acquires the lock unless the current thread is |
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* {@linkplain Thread#interrupt interrupted}. |
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* |
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* <p>Acquires the lock if it is not held by another thread and returns |
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* immediately, setting the lock hold count to one. |
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* |
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* <p>If the current thread already holds this lock then the hold count |
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* is incremented by one and the method returns immediately. |
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* |
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* <p>If the lock is held by another thread then the |
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* current thread becomes disabled for thread scheduling |
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* purposes and lies dormant until one of two things happens: |
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* |
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* <ul> |
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* |
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* <li>The lock is acquired by the current thread; or |
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* |
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* <li>Some other thread {@linkplain Thread#interrupt interrupts} the |
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* current thread. |
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* |
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* </ul> |
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* |
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* <p>If the lock is acquired by the current thread then the lock hold |
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* count is set to one. |
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* |
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* <p>If the current thread: |
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* |
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* <ul> |
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* |
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* <li>has its interrupted status set on entry to this method; or |
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* |
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* <li>is {@linkplain Thread#interrupt interrupted} while acquiring |
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* the lock, |
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* |
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* </ul> |
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* |
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* then {@link InterruptedException} is thrown and the current thread's |
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* interrupted status is cleared. |
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* |
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* <p>In this implementation, as this method is an explicit |
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* interruption point, preference is given to responding to the |
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* interrupt over normal or reentrant acquisition of the lock. |
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* |
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* @throws InterruptedException if the current thread is interrupted |
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*/ |
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public void lockInterruptibly() throws InterruptedException { |
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sync.acquireInterruptibly(1); |
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} |
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|
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/** |
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* Acquires the lock only if it is not held by another thread at the time |
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* of invocation. |
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* |
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* <p>Acquires the lock if it is not held by another thread and |
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* returns immediately with the value {@code true}, setting the |
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* lock hold count to one. Even when this lock has been set to use a |
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* fair ordering policy, a call to {@code tryLock()} <em>will</em> |
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* immediately acquire the lock if it is available, whether or not |
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* other threads are currently waiting for the lock. |
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* This "barging" behavior can be useful in certain |
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* circumstances, even though it breaks fairness. If you want to honor |
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* the fairness setting for this lock, then use |
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* {@link #tryLock(long, TimeUnit) tryLock(0, TimeUnit.SECONDS) } |
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* which is almost equivalent (it also detects interruption). |
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* |
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* <p>If the current thread already holds this lock then the hold |
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* count is incremented by one and the method returns {@code true}. |
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* |
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* <p>If the lock is held by another thread then this method will return |
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* immediately with the value {@code false}. |
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* |
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* @return {@code true} if the lock was free and was acquired by the |
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* current thread, or the lock was already held by the current |
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* thread; and {@code false} otherwise |
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*/ |
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public boolean tryLock() { |
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return sync.nonfairTryAcquire(1); |
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} |
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|
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/** |
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* Acquires the lock if it is not held by another thread within the given |
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* waiting time and the current thread has not been |
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* {@linkplain Thread#interrupt interrupted}. |
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* |
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* <p>Acquires the lock if it is not held by another thread and returns |
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* immediately with the value {@code true}, setting the lock hold count |
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* to one. If this lock has been set to use a fair ordering policy then |
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* an available lock <em>will not</em> be acquired if any other threads |
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* are waiting for the lock. This is in contrast to the {@link #tryLock()} |
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* method. If you want a timed {@code tryLock} that does permit barging on |
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* a fair lock then combine the timed and un-timed forms together: |
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* |
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* <pre> {@code |
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* if (lock.tryLock() || |
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* lock.tryLock(timeout, unit)) { |
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* ... |
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* }}</pre> |
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* |
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* <p>If the current thread |
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* already holds this lock then the hold count is incremented by one and |
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* the method returns {@code true}. |
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* |
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* <p>If the lock is held by another thread then the |
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* current thread becomes disabled for thread scheduling |
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* purposes and lies dormant until one of three things happens: |
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* |
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* <ul> |
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* |
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* <li>The lock is acquired by the current thread; or |
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* |
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* <li>Some other thread {@linkplain Thread#interrupt interrupts} |
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* the current thread; or |
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* |
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* <li>The specified waiting time elapses |
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* |
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* </ul> |
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* |
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* <p>If the lock is acquired then the value {@code true} is returned and |
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* the lock hold count is set to one. |
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* |
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* <p>If the current thread: |
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* |
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* <ul> |
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* |
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* <li>has its interrupted status set on entry to this method; or |
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* |
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* <li>is {@linkplain Thread#interrupt interrupted} while |
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* acquiring the lock, |
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* |
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* </ul> |
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* then {@link InterruptedException} is thrown and the current thread's |
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* interrupted status is cleared. |
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* |
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* <p>If the specified waiting time elapses then the value {@code false} |
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* is returned. If the time is less than or equal to zero, the method |
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* will not wait at all. |
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* |
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* <p>In this implementation, as this method is an explicit |
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* interruption point, preference is given to responding to the |
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* interrupt over normal or reentrant acquisition of the lock, and |
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* over reporting the elapse of the waiting time. |
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* |
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* @param timeout the time to wait for the lock |
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* @param unit the time unit of the timeout argument |
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* @return {@code true} if the lock was free and was acquired by the |
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* current thread, or the lock was already held by the current |
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* thread; and {@code false} if the waiting time elapsed before |
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* the lock could be acquired |
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* @throws InterruptedException if the current thread is interrupted |
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* @throws NullPointerException if the time unit is null |
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*/ |
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public boolean tryLock(long timeout, TimeUnit unit) |
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throws InterruptedException { |
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return sync.tryAcquireNanos(1, unit.toNanos(timeout)); |
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} |
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|
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/** |
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* Attempts to release this lock. |
419 |
* |
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* <p>If the current thread is the holder of this lock then the hold |
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* count is decremented. If the hold count is now zero then the lock |
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* is released. If the current thread is not the holder of this |
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* lock then {@link IllegalMonitorStateException} is thrown. |
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* |
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* @throws IllegalMonitorStateException if the current thread does not |
426 |
* hold this lock |
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*/ |
428 |
public void unlock() { |
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sync.release(1); |
430 |
} |
431 |
|
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/** |
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* Returns a {@link Condition} instance for use with this |
434 |
* {@link Lock} instance. |
435 |
* |
436 |
* <p>The returned {@link Condition} instance supports the same |
437 |
* usages as do the {@link Object} monitor methods ({@link |
438 |
* Object#wait() wait}, {@link Object#notify notify}, and {@link |
439 |
* Object#notifyAll notifyAll}) when used with the built-in |
440 |
* monitor lock. |
441 |
* |
442 |
* <ul> |
443 |
* |
444 |
* <li>If this lock is not held when any of the {@link Condition} |
445 |
* {@linkplain Condition#await() waiting} or {@linkplain |
446 |
* Condition#signal signalling} methods are called, then an {@link |
447 |
* IllegalMonitorStateException} is thrown. |
448 |
* |
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* <li>When the condition {@linkplain Condition#await() waiting} |
450 |
* methods are called the lock is released and, before they |
451 |
* return, the lock is reacquired and the lock hold count restored |
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* to what it was when the method was called. |
453 |
* |
454 |
* <li>If a thread is {@linkplain Thread#interrupt interrupted} |
455 |
* while waiting then the wait will terminate, an {@link |
456 |
* InterruptedException} will be thrown, and the thread's |
457 |
* interrupted status will be cleared. |
458 |
* |
459 |
* <li>Waiting threads are signalled in FIFO order. |
460 |
* |
461 |
* <li>The ordering of lock reacquisition for threads returning |
462 |
* from waiting methods is the same as for threads initially |
463 |
* acquiring the lock, which is in the default case not specified, |
464 |
* but for <em>fair</em> locks favors those threads that have been |
465 |
* waiting the longest. |
466 |
* |
467 |
* </ul> |
468 |
* |
469 |
* @return the Condition object |
470 |
*/ |
471 |
public Condition newCondition() { |
472 |
return sync.newCondition(); |
473 |
} |
474 |
|
475 |
/** |
476 |
* Queries the number of holds on this lock by the current thread. |
477 |
* |
478 |
* <p>A thread has a hold on a lock for each lock action that is not |
479 |
* matched by an unlock action. |
480 |
* |
481 |
* <p>The hold count information is typically only used for testing and |
482 |
* debugging purposes. For example, if a certain section of code should |
483 |
* not be entered with the lock already held then we can assert that |
484 |
* fact: |
485 |
* |
486 |
* <pre> {@code |
487 |
* class X { |
488 |
* ReentrantLock lock = new ReentrantLock(); |
489 |
* // ... |
490 |
* public void m() { |
491 |
* assert lock.getHoldCount() == 0; |
492 |
* lock.lock(); |
493 |
* try { |
494 |
* // ... method body |
495 |
* } finally { |
496 |
* lock.unlock(); |
497 |
* } |
498 |
* } |
499 |
* }}</pre> |
500 |
* |
501 |
* @return the number of holds on this lock by the current thread, |
502 |
* or zero if this lock is not held by the current thread |
503 |
*/ |
504 |
public int getHoldCount() { |
505 |
return sync.getHoldCount(); |
506 |
} |
507 |
|
508 |
/** |
509 |
* Queries if this lock is held by the current thread. |
510 |
* |
511 |
* <p>Analogous to the {@link Thread#holdsLock(Object)} method for |
512 |
* built-in monitor locks, this method is typically used for |
513 |
* debugging and testing. For example, a method that should only be |
514 |
* called while a lock is held can assert that this is the case: |
515 |
* |
516 |
* <pre> {@code |
517 |
* class X { |
518 |
* ReentrantLock lock = new ReentrantLock(); |
519 |
* // ... |
520 |
* |
521 |
* public void m() { |
522 |
* assert lock.isHeldByCurrentThread(); |
523 |
* // ... method body |
524 |
* } |
525 |
* }}</pre> |
526 |
* |
527 |
* <p>It can also be used to ensure that a reentrant lock is used |
528 |
* in a non-reentrant manner, for example: |
529 |
* |
530 |
* <pre> {@code |
531 |
* class X { |
532 |
* ReentrantLock lock = new ReentrantLock(); |
533 |
* // ... |
534 |
* |
535 |
* public void m() { |
536 |
* assert !lock.isHeldByCurrentThread(); |
537 |
* lock.lock(); |
538 |
* try { |
539 |
* // ... method body |
540 |
* } finally { |
541 |
* lock.unlock(); |
542 |
* } |
543 |
* } |
544 |
* }}</pre> |
545 |
* |
546 |
* @return {@code true} if current thread holds this lock and |
547 |
* {@code false} otherwise |
548 |
*/ |
549 |
public boolean isHeldByCurrentThread() { |
550 |
return sync.isHeldExclusively(); |
551 |
} |
552 |
|
553 |
/** |
554 |
* Queries if this lock is held by any thread. This method is |
555 |
* designed for use in monitoring of the system state, |
556 |
* not for synchronization control. |
557 |
* |
558 |
* @return {@code true} if any thread holds this lock and |
559 |
* {@code false} otherwise |
560 |
*/ |
561 |
public boolean isLocked() { |
562 |
return sync.isLocked(); |
563 |
} |
564 |
|
565 |
/** |
566 |
* Returns {@code true} if this lock has fairness set true. |
567 |
* |
568 |
* @return {@code true} if this lock has fairness set true |
569 |
*/ |
570 |
public final boolean isFair() { |
571 |
return sync instanceof FairSync; |
572 |
} |
573 |
|
574 |
/** |
575 |
* Returns the thread that currently owns this lock, or |
576 |
* {@code null} if not owned. When this method is called by a |
577 |
* thread that is not the owner, the return value reflects a |
578 |
* best-effort approximation of current lock status. For example, |
579 |
* the owner may be momentarily {@code null} even if there are |
580 |
* threads trying to acquire the lock but have not yet done so. |
581 |
* This method is designed to facilitate construction of |
582 |
* subclasses that provide more extensive lock monitoring |
583 |
* facilities. |
584 |
* |
585 |
* @return the owner, or {@code null} if not owned |
586 |
*/ |
587 |
protected Thread getOwner() { |
588 |
return sync.getOwner(); |
589 |
} |
590 |
|
591 |
/** |
592 |
* Queries whether any threads are waiting to acquire this lock. Note that |
593 |
* because cancellations may occur at any time, a {@code true} |
594 |
* return does not guarantee that any other thread will ever |
595 |
* acquire this lock. This method is designed primarily for use in |
596 |
* monitoring of the system state. |
597 |
* |
598 |
* @return {@code true} if there may be other threads waiting to |
599 |
* acquire the lock |
600 |
*/ |
601 |
public final boolean hasQueuedThreads() { |
602 |
return sync.hasQueuedThreads(); |
603 |
} |
604 |
|
605 |
/** |
606 |
* Queries whether the given thread is waiting to acquire this |
607 |
* lock. Note that because cancellations may occur at any time, a |
608 |
* {@code true} return does not guarantee that this thread |
609 |
* will ever acquire this lock. This method is designed primarily for use |
610 |
* in monitoring of the system state. |
611 |
* |
612 |
* @param thread the thread |
613 |
* @return {@code true} if the given thread is queued waiting for this lock |
614 |
* @throws NullPointerException if the thread is null |
615 |
*/ |
616 |
public final boolean hasQueuedThread(Thread thread) { |
617 |
return sync.isQueued(thread); |
618 |
} |
619 |
|
620 |
/** |
621 |
* Returns an estimate of the number of threads waiting to acquire |
622 |
* this lock. The value is only an estimate because the number of |
623 |
* threads may change dynamically while this method traverses |
624 |
* internal data structures. This method is designed for use in |
625 |
* monitoring system state, not for synchronization control. |
626 |
* |
627 |
* @return the estimated number of threads waiting for this lock |
628 |
*/ |
629 |
public final int getQueueLength() { |
630 |
return sync.getQueueLength(); |
631 |
} |
632 |
|
633 |
/** |
634 |
* Returns a collection containing threads that may be waiting to |
635 |
* acquire this lock. Because the actual set of threads may change |
636 |
* dynamically while constructing this result, the returned |
637 |
* collection is only a best-effort estimate. The elements of the |
638 |
* returned collection are in no particular order. This method is |
639 |
* designed to facilitate construction of subclasses that provide |
640 |
* more extensive monitoring facilities. |
641 |
* |
642 |
* @return the collection of threads |
643 |
*/ |
644 |
protected Collection<Thread> getQueuedThreads() { |
645 |
return sync.getQueuedThreads(); |
646 |
} |
647 |
|
648 |
/** |
649 |
* Queries whether any threads are waiting on the given condition |
650 |
* associated with this lock. Note that because timeouts and |
651 |
* interrupts may occur at any time, a {@code true} return does |
652 |
* not guarantee that a future {@code signal} will awaken any |
653 |
* threads. This method is designed primarily for use in |
654 |
* monitoring of the system state. |
655 |
* |
656 |
* @param condition the condition |
657 |
* @return {@code true} if there are any waiting threads |
658 |
* @throws IllegalMonitorStateException if this lock is not held |
659 |
* @throws IllegalArgumentException if the given condition is |
660 |
* not associated with this lock |
661 |
* @throws NullPointerException if the condition is null |
662 |
*/ |
663 |
public boolean hasWaiters(Condition condition) { |
664 |
if (condition == null) |
665 |
throw new NullPointerException(); |
666 |
if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject)) |
667 |
throw new IllegalArgumentException("not owner"); |
668 |
return sync.hasWaiters((AbstractQueuedSynchronizer.ConditionObject)condition); |
669 |
} |
670 |
|
671 |
/** |
672 |
* Returns an estimate of the number of threads waiting on the |
673 |
* given condition associated with this lock. Note that because |
674 |
* timeouts and interrupts may occur at any time, the estimate |
675 |
* serves only as an upper bound on the actual number of waiters. |
676 |
* This method is designed for use in monitoring of the system |
677 |
* state, not for synchronization control. |
678 |
* |
679 |
* @param condition the condition |
680 |
* @return the estimated number of waiting threads |
681 |
* @throws IllegalMonitorStateException if this lock is not held |
682 |
* @throws IllegalArgumentException if the given condition is |
683 |
* not associated with this lock |
684 |
* @throws NullPointerException if the condition is null |
685 |
*/ |
686 |
public int getWaitQueueLength(Condition condition) { |
687 |
if (condition == null) |
688 |
throw new NullPointerException(); |
689 |
if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject)) |
690 |
throw new IllegalArgumentException("not owner"); |
691 |
return sync.getWaitQueueLength((AbstractQueuedSynchronizer.ConditionObject)condition); |
692 |
} |
693 |
|
694 |
/** |
695 |
* Returns a collection containing those threads that may be |
696 |
* waiting on the given condition associated with this lock. |
697 |
* Because the actual set of threads may change dynamically while |
698 |
* constructing this result, the returned collection is only a |
699 |
* best-effort estimate. The elements of the returned collection |
700 |
* are in no particular order. This method is designed to |
701 |
* facilitate construction of subclasses that provide more |
702 |
* extensive condition monitoring facilities. |
703 |
* |
704 |
* @param condition the condition |
705 |
* @return the collection of threads |
706 |
* @throws IllegalMonitorStateException if this lock is not held |
707 |
* @throws IllegalArgumentException if the given condition is |
708 |
* not associated with this lock |
709 |
* @throws NullPointerException if the condition is null |
710 |
*/ |
711 |
protected Collection<Thread> getWaitingThreads(Condition condition) { |
712 |
if (condition == null) |
713 |
throw new NullPointerException(); |
714 |
if (!(condition instanceof AbstractQueuedSynchronizer.ConditionObject)) |
715 |
throw new IllegalArgumentException("not owner"); |
716 |
return sync.getWaitingThreads((AbstractQueuedSynchronizer.ConditionObject)condition); |
717 |
} |
718 |
|
719 |
/** |
720 |
* Returns a string identifying this lock, as well as its lock state. |
721 |
* The state, in brackets, includes either the String {@code "Unlocked"} |
722 |
* or the String {@code "Locked by"} followed by the |
723 |
* {@linkplain Thread#getName name} of the owning thread. |
724 |
* |
725 |
* @return a string identifying this lock, as well as its lock state |
726 |
*/ |
727 |
public String toString() { |
728 |
Thread o = sync.getOwner(); |
729 |
return super.toString() + ((o == null) ? |
730 |
"[Unlocked]" : |
731 |
"[Locked by thread " + o.getName() + "]"); |
732 |
} |
733 |
} |