1adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project/* 229957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 329957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 429957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * This code is free software; you can redistribute it and/or modify it 529957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * under the terms of the GNU General Public License version 2 only, as 629957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * published by the Free Software Foundation. Oracle designates this 729957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * particular file as subject to the "Classpath" exception as provided 829957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * by Oracle in the LICENSE file that accompanied this code. 929957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 1029957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * This code is distributed in the hope that it will be useful, but WITHOUT 1129957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 1229957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 1329957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * version 2 for more details (a copy is included in the LICENSE file that 1429957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * accompanied this code). 1529957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 1629957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * You should have received a copy of the GNU General Public License version 1729957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 2 along with this work; if not, write to the Free Software Foundation, 1829957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 1929957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 2029957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2129957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * or visit www.oracle.com if you need additional information or have any 2229957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * questions. 2329957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer */ 2429957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer 2529957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer/* 2629957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * This file is available under and governed by the GNU General Public 2729957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * License version 2 only, as published by the Free Software Foundation. 2829957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * However, the following notice accompanied the original version of this 2929957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * file: 3029957558cf0db700bfaae360a80c42dc3871d0e5Tobias Thierer * 31adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Written by Doug Lea with assistance from members of JCP JSR-166 32adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Expert Group and released to the public domain, as explained at 33a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * http://creativecommons.org/publicdomain/zero/1.0/ 34adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project */ 35adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 36adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Projectpackage java.util.concurrent.locks; 37edf43d27e240d82106f39ae91404963c23987234Narayan Kamath 38adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Projectimport java.util.concurrent.TimeUnit; 39adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 40adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project/** 41bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code Lock} implementations provide more extensive locking 42bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * operations than can be obtained using {@code synchronized} methods 43adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * and statements. They allow more flexible structuring, may have 44adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * quite different properties, and may support multiple associated 45adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * {@link Condition} objects. 46adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 47adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>A lock is a tool for controlling access to a shared resource by 48adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * multiple threads. Commonly, a lock provides exclusive access to a 49adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * shared resource: only one thread at a time can acquire the lock and 50adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * all access to the shared resource requires that the lock be 51adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * acquired first. However, some locks may allow concurrent access to 52bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * a shared resource, such as the read lock of a {@link ReadWriteLock}. 53adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 54bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>The use of {@code synchronized} methods or statements provides 55adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * access to the implicit monitor lock associated with every object, but 56adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * forces all lock acquisition and release to occur in a block-structured way: 57adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * when multiple locks are acquired they must be released in the opposite 58adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * order, and all locks must be released in the same lexical scope in which 59adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * they were acquired. 60adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 61bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>While the scoping mechanism for {@code synchronized} methods 62adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * and statements makes it much easier to program with monitor locks, 63adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * and helps avoid many common programming errors involving locks, 64adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * there are occasions where you need to work with locks in a more 65adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * flexible way. For example, some algorithms for traversing 66adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * concurrently accessed data structures require the use of 67adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * "hand-over-hand" or "chain locking": you 68adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * acquire the lock of node A, then node B, then release A and acquire 69adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * C, then release B and acquire D and so on. Implementations of the 70bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code Lock} interface enable the use of such techniques by 71adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * allowing a lock to be acquired and released in different scopes, 72adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * and allowing multiple locks to be acquired and released in any 73adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * order. 74adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 75adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>With this increased flexibility comes additional 76adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * responsibility. The absence of block-structured locking removes the 77bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * automatic release of locks that occurs with {@code synchronized} 78adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * methods and statements. In most cases, the following idiom 79adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * should be used: 80adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 81b8b75116273ecfdb8ffdd1869b1c0dd04570a95ePrzemyslaw Szczepaniak * <pre> {@code 82a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * Lock l = ...; 83a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * l.lock(); 84a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * try { 85a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * // access the resource protected by this lock 86a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * } finally { 87a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * l.unlock(); 88a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * }}</pre> 89adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 90adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * When locking and unlocking occur in different scopes, care must be 91adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * taken to ensure that all code that is executed while the lock is 92adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * held is protected by try-finally or try-catch to ensure that the 93adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * lock is released when necessary. 94adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 95bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>{@code Lock} implementations provide additional functionality 96bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * over the use of {@code synchronized} methods and statements by 97adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * providing a non-blocking attempt to acquire a lock ({@link 98adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * #tryLock()}), an attempt to acquire the lock that can be 99adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * interrupted ({@link #lockInterruptibly}, and an attempt to acquire 100adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * the lock that can timeout ({@link #tryLock(long, TimeUnit)}). 101adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 102bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>A {@code Lock} class can also provide behavior and semantics 103adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * that is quite different from that of the implicit monitor lock, 104adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * such as guaranteed ordering, non-reentrant usage, or deadlock 105adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * detection. If an implementation provides such specialized semantics 106adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * then the implementation must document those semantics. 107adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 108bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>Note that {@code Lock} instances are just normal objects and can 109bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * themselves be used as the target in a {@code synchronized} statement. 110adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Acquiring the 111bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * monitor lock of a {@code Lock} instance has no specified relationship 112bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * with invoking any of the {@link #lock} methods of that instance. 113bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * It is recommended that to avoid confusion you never use {@code Lock} 114adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * instances in this way, except within their own implementation. 115adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 116bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>Except where noted, passing a {@code null} value for any 117adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * parameter will result in a {@link NullPointerException} being 118adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * thrown. 119adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 120adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <h3>Memory Synchronization</h3> 121bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 122bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>All {@code Lock} implementations <em>must</em> enforce the same 123bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * memory synchronization semantics as provided by the built-in monitor 12491770798d8b9280d48d30df2ed7f63b3ed9b036fCalin Juravle * lock, as described in 125b8b75116273ecfdb8ffdd1869b1c0dd04570a95ePrzemyslaw Szczepaniak * <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.4"> 126b8b75116273ecfdb8ffdd1869b1c0dd04570a95ePrzemyslaw Szczepaniak * Chapter 17 of 127b8b75116273ecfdb8ffdd1869b1c0dd04570a95ePrzemyslaw Szczepaniak * <cite>The Java™ Language Specification</cite></a>: 128adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <ul> 129bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>A successful {@code lock} operation has the same memory 130bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * synchronization effects as a successful <em>Lock</em> action. 131bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>A successful {@code unlock} operation has the same 132bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * memory synchronization effects as a successful <em>Unlock</em> action. 133adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * </ul> 134adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 135adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Unsuccessful locking and unlocking operations, and reentrant 136adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * locking/unlocking operations, do not require any memory 137adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * synchronization effects. 138adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 139adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <h3>Implementation Considerations</h3> 140adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 14191770798d8b9280d48d30df2ed7f63b3ed9b036fCalin Juravle * <p>The three forms of lock acquisition (interruptible, 142adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * non-interruptible, and timed) may differ in their performance 143adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * characteristics, ordering guarantees, or other implementation 144adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * qualities. Further, the ability to interrupt the <em>ongoing</em> 145bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * acquisition of a lock may not be available in a given {@code Lock} 146adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * class. Consequently, an implementation is not required to define 147adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * exactly the same guarantees or semantics for all three forms of 148adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * lock acquisition, nor is it required to support interruption of an 149adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * ongoing lock acquisition. An implementation is required to clearly 150adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * document the semantics and guarantees provided by each of the 151adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * locking methods. It must also obey the interruption semantics as 152adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * defined in this interface, to the extent that interruption of lock 153adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * acquisition is supported: which is either totally, or only on 154adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * method entry. 155adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 156bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>As interruption generally implies cancellation, and checks for 157adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * interruption are often infrequent, an implementation can favor responding 158adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * to an interrupt over normal method return. This is true even if it can be 159adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * shown that the interrupt occurred after another action may have unblocked 160bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * the thread. An implementation should document this behavior. 161adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 162adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @see ReentrantLock 163adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @see Condition 164adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @see ReadWriteLock 165adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 166adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @since 1.5 167adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @author Doug Lea 168bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 169adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Projectpublic interface Lock { 170adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 171adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 172adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Acquires the lock. 173bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 174bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>If the lock is not available then the current thread becomes 175bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * disabled for thread scheduling purposes and lies dormant until the 176bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * lock has been acquired. 177bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 178adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p><b>Implementation Considerations</b> 179adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 180bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>A {@code Lock} implementation may be able to detect erroneous use 181bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * of the lock, such as an invocation that would cause deadlock, and 182bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * may throw an (unchecked) exception in such circumstances. The 183bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * circumstances and the exception type must be documented by that 184bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code Lock} implementation. 185bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 186adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project void lock(); 187adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 188adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 189bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * Acquires the lock unless the current thread is 190bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@linkplain Thread#interrupt interrupted}. 191bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 192adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>Acquires the lock if it is available and returns immediately. 193bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 194bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>If the lock is not available then the current thread becomes 195bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * disabled for thread scheduling purposes and lies dormant until 196bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * one of two things happens: 197bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 198adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <ul> 199adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <li>The lock is acquired by the current thread; or 200bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>Some other thread {@linkplain Thread#interrupt interrupts} the 201bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * current thread, and interruption of lock acquisition is supported. 202adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * </ul> 203bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 204adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>If the current thread: 205adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <ul> 206bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>has its interrupted status set on entry to this method; or 207bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>is {@linkplain Thread#interrupt interrupted} while acquiring the 208bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * lock, and interruption of lock acquisition is supported, 209adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * </ul> 210bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * then {@link InterruptedException} is thrown and the current thread's 211bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * interrupted status is cleared. 212adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 213adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p><b>Implementation Considerations</b> 214adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 215adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>The ability to interrupt a lock acquisition in some 216adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * implementations may not be possible, and if possible may be an 217adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * expensive operation. The programmer should be aware that this 218adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * may be the case. An implementation should document when this is 219adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * the case. 220adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 221adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>An implementation can favor responding to an interrupt over 222adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * normal method return. 223adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 224bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>A {@code Lock} implementation may be able to detect 225adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * erroneous use of the lock, such as an invocation that would 226adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * cause deadlock, and may throw an (unchecked) exception in such 227adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * circumstances. The circumstances and the exception type must 228bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * be documented by that {@code Lock} implementation. 229adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 230bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @throws InterruptedException if the current thread is 231bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * interrupted while acquiring the lock (and interruption 23291770798d8b9280d48d30df2ed7f63b3ed9b036fCalin Juravle * of lock acquisition is supported) 233bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 234adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project void lockInterruptibly() throws InterruptedException; 235adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 236adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 237adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Acquires the lock only if it is free at the time of invocation. 238bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 239adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>Acquires the lock if it is available and returns immediately 240bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * with the value {@code true}. 241bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * If the lock is not available then this method will return 242bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * immediately with the value {@code false}. 243bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 244adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>A typical usage idiom for this method would be: 245b8b75116273ecfdb8ffdd1869b1c0dd04570a95ePrzemyslaw Szczepaniak * <pre> {@code 246a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * Lock lock = ...; 247a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * if (lock.tryLock()) { 248a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * try { 249a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * // manipulate protected state 250a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * } finally { 251a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * lock.unlock(); 252a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * } 253a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * } else { 254a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * // perform alternative actions 255a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * }}</pre> 256a807b4d808d2591894daf13aab179b2e9c46a2f5Jesse Wilson * 257adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * This usage ensures that the lock is unlocked if it was acquired, and 258adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * doesn't try to unlock if the lock was not acquired. 259adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 260bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @return {@code true} if the lock was acquired and 261bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code false} otherwise 262bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 263adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project boolean tryLock(); 264adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 265adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 266adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Acquires the lock if it is free within the given waiting time and the 267bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * current thread has not been {@linkplain Thread#interrupt interrupted}. 268adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 269adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>If the lock is available this method returns immediately 270bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * with the value {@code true}. 271adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * If the lock is not available then 272bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * the current thread becomes disabled for thread scheduling 273adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * purposes and lies dormant until one of three things happens: 274adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <ul> 275adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <li>The lock is acquired by the current thread; or 276bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>Some other thread {@linkplain Thread#interrupt interrupts} the 277bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * current thread, and interruption of lock acquisition is supported; or 278adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <li>The specified waiting time elapses 279adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * </ul> 280bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 281bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>If the lock is acquired then the value {@code true} is returned. 282bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 283adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>If the current thread: 284adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <ul> 285bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>has its interrupted status set on entry to this method; or 286bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <li>is {@linkplain Thread#interrupt interrupted} while acquiring 287bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * the lock, and interruption of lock acquisition is supported, 288adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * </ul> 289bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * then {@link InterruptedException} is thrown and the current thread's 290bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * interrupted status is cleared. 291bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 292bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>If the specified waiting time elapses then the value {@code false} 293adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * is returned. 294bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * If the time is 295adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * less than or equal to zero, the method will not wait at all. 296adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 297adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p><b>Implementation Considerations</b> 298bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 299adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p>The ability to interrupt a lock acquisition in some implementations 300bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * may not be possible, and if possible may 301bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * be an expensive operation. 302adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * The programmer should be aware that this may be the case. An 303adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * implementation should document when this is the case. 304bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 305bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>An implementation can favor responding to an interrupt over normal 306adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * method return, or reporting a timeout. 307bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 308bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>A {@code Lock} implementation may be able to detect 309bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * erroneous use of the lock, such as an invocation that would cause 310bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * deadlock, and may throw an (unchecked) exception in such circumstances. 311bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * The circumstances and the exception type must be documented by that 312bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code Lock} implementation. 313adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 314adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @param time the maximum time to wait for the lock 315bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @param unit the time unit of the {@code time} argument 316bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @return {@code true} if the lock was acquired and {@code false} 317bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * if the waiting time elapsed before the lock was acquired 318adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * 319adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * @throws InterruptedException if the current thread is interrupted 320bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * while acquiring the lock (and interruption of lock 321bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * acquisition is supported) 322bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 323adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project boolean tryLock(long time, TimeUnit unit) throws InterruptedException; 324adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 325adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 326adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Releases the lock. 327bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 328adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p><b>Implementation Considerations</b> 329bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 330bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>A {@code Lock} implementation will usually impose 331adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * restrictions on which thread can release a lock (typically only the 332adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * holder of the lock can release it) and may throw 333adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * an (unchecked) exception if the restriction is violated. 334adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * Any restrictions and the exception 335bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * type must be documented by that {@code Lock} implementation. 336bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 337adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project void unlock(); 338adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project 339adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project /** 340bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * Returns a new {@link Condition} instance that is bound to this 341bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * {@code Lock} instance. 342bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 343bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>Before waiting on the condition the lock must be held by the 344bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * current thread. 345bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * A call to {@link Condition#await()} will atomically release the lock 346adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * before waiting and re-acquire the lock before the wait returns. 347bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 348adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * <p><b>Implementation Considerations</b> 349bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 350bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * <p>The exact operation of the {@link Condition} instance depends on 351bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * the {@code Lock} implementation and must be documented by that 352adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project * implementation. 353bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * 354bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @return A new {@link Condition} instance for this {@code Lock} instance 355bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * @throws UnsupportedOperationException if this {@code Lock} 356bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson * implementation does not support conditions 357bba8d1acd6dfff06c94d761c67a30154ca5ca5dfJesse Wilson */ 358adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project Condition newCondition(); 359adc854b798c1cfe3bfd4c27d68d5cee38ca617daThe Android Open Source Project} 360