Mercurial > hg4j
view src/org/tmatesoft/hg/util/Adaptable.java @ 396:0ae53c32ecef
Straighten out exceptions thrown when file access failed - three is too much
author | Artem Tikhomirov <tikhomirov.artem@gmail.com> |
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date | Thu, 23 Feb 2012 01:06:24 +0100 |
parents | 91d75e1bac9f |
children |
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/* * Copyright (c) 2011 TMate Software Ltd * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2 of the License. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * For information on how to redistribute this software under * the terms of a license other than GNU General Public License * contact TMate Software at support@hg4j.com */ package org.tmatesoft.hg.util; /** * Extension mechanism. * * @author Artem Tikhomirov * @author TMate Software Ltd. */ public interface Adaptable { <T> T getAdapter(Class<T> adapterClass); class Factory<T> { private final Class<T> adapterClass; public Factory(Class<T> adapterClass) { assert adapterClass != null; this.adapterClass = adapterClass; } public T get(Object target) { return getAdapter(target, adapterClass, null); } public T get(Object target, T defaultValue) { return getAdapter(target, adapterClass, defaultValue); } /** * Try to adapt target to specified class, resort to defaultValue when not possible. * Instance lookup order is as follows: first, target is checked for being {@link Adaptable} and, if yes, * consulted for adapter. Then, plain {@link Class#isInstance(Object) instanceof} checks if target itself is * of desired type. {@link Adaptable} check comes first to allow classed that are in fact <code>instanceof</code> * desired type to respond to the demand conditionally * * @param target object to adapt, <code>null</code> value, although meaningless, is tolerable. * @param adapterClass desired target class * @param defaultValue value to use if target cannot be adapted to desired class, may be <code>null</code> * @return instance of the desired class */ public static <C> C getAdapter(Object target, Class<C> adapterClass, C defaultValue) { if (target instanceof Adaptable) { return ((Adaptable) target).getAdapter(adapterClass); } if (adapterClass.isInstance(target)) { return adapterClass.cast(target); } return defaultValue; } } }