001: /*
002: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003: *
004: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * The contents of this file are subject to the terms of either the GNU
007: * General Public License Version 2 only ("GPL") or the Common
008: * Development and Distribution License("CDDL") (collectively, the
009: * "License"). You may not use this file except in compliance with the
010: * License. You can obtain a copy of the License at
011: * http://www.netbeans.org/cddl-gplv2.html
012: * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
013: * specific language governing permissions and limitations under the
014: * License. When distributing the software, include this License Header
015: * Notice in each file and include the License file at
016: * nbbuild/licenses/CDDL-GPL-2-CP. Sun designates this
017: * particular file as subject to the "Classpath" exception as provided
018: * by Sun in the GPL Version 2 section of the License file that
019: * accompanied this code. If applicable, add the following below the
020: * License Header, with the fields enclosed by brackets [] replaced by
021: * your own identifying information:
022: * "Portions Copyrighted [year] [name of copyright owner]"
023: *
024: * Contributor(s):
025: *
026: * The Original Software is NetBeans. The Initial Developer of the Original
027: * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
028: * Microsystems, Inc. All Rights Reserved.
029: *
030: * If you wish your version of this file to be governed by only the CDDL
031: * or only the GPL Version 2, indicate your decision by adding
032: * "[Contributor] elects to include this software in this distribution
033: * under the [CDDL or GPL Version 2] license." If you do not indicate a
034: * single choice of license, a recipient has the option to distribute
035: * your version of this file under either the CDDL, the GPL Version 2 or
036: * to extend the choice of license to its licensees as provided above.
037: * However, if you add GPL Version 2 code and therefore, elected the GPL
038: * Version 2 license, then the option applies only if the new code is
039: * made subject to such option by the copyright holder.
040: */
041:
042: package threaddemo.locking;
043:
044: // XXX add support for read/writeSoon(Runnable)?
045: // XXX why bother with InvocationTargetException?
046:
047: /**
048: * Some kind of a lock, with support for possible read and write modes.
049: * <P>
050: * Examples of use:
051: *
052: * <pre>
053: * Lock m = Locks.readWriteLock("foo", 0);
054: *
055: * // Grant write access, compute an integer and return it:
056: * return m.write(new LockAction<Integer>() {
057: * public Integer run() {
058: * return 1;
059: * }
060: * });
061: *
062: * // Obtain read access, do some computation, possibly throw an IOException:
063: * m.read(new LockExceptionAction<Void,IOException>() {
064: * public Void run() throws IOException {
065: * if (...) throw new IOException();
066: * return null;
067: * }
068: * });
069: * </pre>
070: *
071: * @see Locks
072: * @author Jesse Glick
073: */
074: public interface RWLock {
075:
076: /** Run an action only with read access.
077: * @param action the action to perform
078: * @return the object returned from {@link LockAction#run}
079: */
080: <T> T read(LockAction<T> action);
081:
082: /** Run an action with read access and possibly throw a checked exception.
083: * Note that <em>runtime exceptions</em> are always passed through, and neither
084: * require this invocation style, nor are encapsulated.
085: * @param action the action to execute
086: * @return the object returned from {@link LockExceptionAction#run}
087: * @throws E a checked exception, if any
088: * @throws RuntimeException if any runtime exception is thrown from the run method
089: * @see #read(LockAction)
090: */
091: <T, E extends Exception> T read(LockExceptionAction<T, E> action)
092: throws E;
093:
094: /** Run an action with read access, returning no result.
095: * @param action the action to perform
096: * @see #read(LockAction)
097: */
098: void read(Runnable action);
099:
100: /**
101: * Run an action asynch with read access.
102: * @param action the action to perform
103: * @see #read(Runnable)
104: */
105: void readLater(Runnable action);
106:
107: /**
108: * Run an action with write access.
109: * <p><strong>May not be called while holding read access.</strong>
110: * @param action the action to perform
111: * @return the result of {@link LockAction#run}
112: */
113: <T> T write(LockAction<T> action);
114:
115: /**
116: * Run an action with write access and possibly throw an exception.
117: * <p><strong>May not be called while holding read access.</strong>
118: * @param action the action to execute
119: * @return the result of {@link LockExceptionAction#run}
120: * @throws E a checked exception, if any
121: * @throws RuntimeException if a runtime exception is thrown in the action
122: * @see #write(LockAction)
123: * @see #read(LockExceptionAction)
124: */
125: <T, E extends Exception> T write(LockExceptionAction<T, E> action)
126: throws E;
127:
128: /**
129: * Run an action with write access and return no result.
130: * @param action the action to perform
131: * @see #write(LockAction)
132: * @see #read(Runnable)
133: */
134: void write(Runnable action);
135:
136: /**
137: * Run an action asynchronously with write access.
138: * @param action the action to perform
139: * @see #write(LockAction)
140: * @see #readLater(Runnable)
141: */
142: void writeLater(Runnable action);
143:
144: /**
145: * Check if the current thread is holding a read or write lock.
146: * @return true if either read or write access is available
147: */
148: boolean canRead();
149:
150: /**
151: * Check if the current thread is holding the write lock.
152: * Note that this will be false in case write access was entered and then
153: * read access was entered inside of that, until the nested read access is
154: * again exited.
155: * @return true if write access is available
156: */
157: boolean canWrite();
158:
159: }
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