| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| LazyRunnable.java | 0% | 16.7% | 33.3% | 15.4% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.lambda; | |
| 36 | ||
| 37 | /** | |
| 38 | * <p>A block of code that executes at most once. The first invocation of {@code run()} runs the code; | |
| 39 | * subsequent invocations are no-ops. (If an exception occurs during evaluation, the nested runnable will be | |
| 40 | * evaluated again on a subsequent invocation.)</p> | |
| 41 | * | |
| 42 | * <p>Evaluation is thread-safe: locking guarantees that the nested code will never be run (and terminate | |
| 43 | * normally) twice. Thus, if two threads invoke {@code run()} for the first time simultaneously, one will | |
| 44 | * block until the other completes, and then act as a no-op.</p> | |
| 45 | * | |
| 46 | * @see LazyThunk | |
| 47 | */ | |
| 48 | public class LazyRunnable implements Runnable { | |
| 49 | ||
| 50 | private Runnable _block; | |
| 51 | ||
| 52 | 2 | public LazyRunnable(Runnable block) { _block = block; } |
| 53 | ||
| 54 | 0 | public void run() { |
| 55 | // double-checked locking is generally incorrect without "volatile"; in this case, though, | |
| 56 | // it works because we're setting a field to "null", not allocating a new object -- in the | |
| 57 | // worst case, threads don't see the null update and we call resolve() more than necessary | |
| 58 | 0 | if (_block != null) { resolve(); } |
| 59 | } | |
| 60 | ||
| 61 | 0 | private synchronized void resolve() { |
| 62 | 0 | if (_block != null) { // verify that the block is still unresolved now that we have a lock |
| 63 | 0 | _block.run(); |
| 64 | 0 | _block = null; |
| 65 | } | |
| 66 | } | |
| 67 | ||
| 68 | } |
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