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| 1 | /* | ||
| 2 | * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package sun.java2d; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * This interface is used to track changes to the complex data of an | ||
| 30 | * object that implements the StateTrackable interface. | ||
| 31 | * <p> | ||
| 32 | * The usage pattern for code accessing the trackable data is as follows: | ||
| 33 | * <pre> | ||
| 34 | * StateTrackable trackedobject; | ||
| 35 | * MyInfo cacheddata; | ||
| 36 | * StateTracker cachetracker; | ||
| 37 | * public synchronized MyInfo getInfoAbout(StateTrackable obj) { | ||
| 38 | * if (trackedobject != obj || !cachetracker.isCurrent()) { | ||
| 39 | * // Note: Always call getStateTracker() before | ||
| 40 | * // caching any data about the objct... | ||
| 41 | * cachetracker = obj.getStateTracker(); | ||
| 42 | * cacheddata = calculateInfoFrom(obj); | ||
| 43 | * trackedobject = obj; | ||
| 44 | * } | ||
| 45 | * return cacheddata; | ||
| 46 | * } | ||
| 47 | * </pre> | ||
| 48 | * Note that the sample code above works correctly regardless of the | ||
| 49 | * {@link StateTrackable.State State} of the complex data of the object, | ||
| 50 | * but it may be inefficient to store precalculated information about | ||
| 51 | * an object whose current {@link StateTrackable.State State} is | ||
| 52 | * {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE} | ||
| 53 | * and it is unnecessary to perform the {@link #isCurrent} test for | ||
| 54 | * data whose current {@link StateTrackable.State State} is | ||
| 55 | * {@link StateTrackable.State#IMMUTABLE IMMUTABLE}. | ||
| 56 | * Optimizations to the sample code for either or both of those terminal | ||
| 57 | * States may be of benefit for some use cases, but is left out of the | ||
| 58 | * example to reduce its complexity. | ||
| 59 | * | ||
| 60 | * @see StateTrackable.State | ||
| 61 | * @since 1.7 | ||
| 62 | */ | ||
| 63 | public interface StateTracker { | ||
| 64 | /** | ||
| 65 | * An implementation of the StateTracker interface which | ||
| 66 | * always returns true. | ||
| 67 | * This implementation is useful for objects whose current | ||
| 68 | * {@link StateTrackable.State State} is | ||
| 69 | * {@link StateTrackable.State#IMMUTABLE IMMUTABLE}. | ||
| 70 | * @since 1.7 | ||
| 71 | */ | ||
| 72 | public StateTracker ALWAYS_CURRENT = new StateTracker() { | ||
| 73 | public boolean isCurrent() { | ||
| 74 | return true; | ||
| 75 | } | ||
| 76 | }; | ||
| 77 | |||
| 78 | /** | ||
| 79 | * An implementation of the StateTracker interface which | ||
| 80 | * always returns false. | ||
| 81 | * This implementation is useful for objects whose current | ||
| 82 | * {@link StateTrackable.State State} is | ||
| 83 | * {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE}. | ||
| 84 | * This implementation may also be useful for some objects | ||
| 85 | * whose current {@link StateTrackable.State State} is | ||
| 86 | * {@link StateTrackable.State#DYNAMIC DYNAMIC}. | ||
| 87 | * @since 1.7 | ||
| 88 | */ | ||
| 89 | public StateTracker NEVER_CURRENT = new StateTracker() { | ||
| 90 | public boolean isCurrent() { | ||
| 91 | return false; | ||
| 92 | } | ||
| 93 | }; | ||
| 94 | |||
| 95 | /** | ||
| 96 | * Returns true iff the contents of the complex data of the | ||
| 97 | * associated StateTrackable object have not changed since | ||
| 98 | * the time that this StateTracker was returned from its | ||
| 99 | * getStateTracker() method. | ||
| 100 | * @see StateTrackable | ||
| 101 | * @since 1.7 | ||
| 102 | */ | ||
| 103 | public boolean isCurrent(); | ||
| 104 | } | ||