| 1 | /* |
| 2 | * $Id: AbstractStepFunction.java 562 2010-11-11 00:28:13Z PSpeed $ |
| 3 | * |
| 4 | * The Filament BSD license. |
| 5 | * |
| 6 | * Copyright (c) 2009-2010, the original author or authors |
| 7 | * |
| 8 | * Redistribution and use in source and binary forms, with or without |
| 9 | * modification, are permitted provided that the following conditions |
| 10 | * are met: |
| 11 | * |
| 12 | * 1) Redistributions of source code must retain the above copyright notice, |
| 13 | * this list of conditions and the following disclaimer. |
| 14 | * 2) Redistributions in binary form must reproduce the above copyright |
| 15 | * notice, this list of conditions and the following disclaimer in the |
| 16 | * documentation and/or other materials provided with the distribution. |
| 17 | * 3) Neither the names "Filament", "fgraph.org", "filamentgraph.org", nor the |
| 18 | * names of its contributors may be used to endorse or promote products |
| 19 | * derived from this software without specific prior written permission. |
| 20 | * |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| 22 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| 25 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 26 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 27 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 28 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 29 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 30 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 31 | * POSSIBILITY OF SUCH DAMAGE. |
| 32 | */ |
| 33 | |
| 34 | package org.fgraph.steps; |
| 35 | |
| 36 | import java.util.*; |
| 37 | |
| 38 | |
| 39 | /** |
| 40 | * Provides some default behavior for parts of the |
| 41 | * StepFunction interface. This is primarily useful for |
| 42 | * StepFunction implementations that need to implement their own |
| 43 | * custom Iterator. Subclasses need only implement the stepIterator() |
| 44 | * method to return an appropriate Iterator. This base class provides an |
| 45 | * Iterable<> wrapper that delegates to it. |
| 46 | * |
| 47 | * @version $Revision: 562 $ |
| 48 | * @author Paul Speed |
| 49 | */ |
| 50 | public abstract class AbstractStepFunction<S,T> implements StepFunction<S,T> |
| 51 | { |
| 52 | /** |
| 53 | * Returns an implementation specific Iterable for the |
| 54 | * supplied starting object. |
| 55 | */ |
| 56 | public Iterable<T> apply( S start ) |
| 57 | { |
| 58 | return new StepIterable(start); |
| 59 | } |
| 60 | |
| 61 | /** |
| 62 | * Implemented by subclasses to provide the actual |
| 63 | * iterator. |
| 64 | */ |
| 65 | protected abstract Iterator<T> stepIterator( S start ); |
| 66 | |
| 67 | /** |
| 68 | * Internal implementation of Iterable that delegates |
| 69 | * to the abstract stepIterator() method. |
| 70 | */ |
| 71 | protected class StepIterable implements Iterable<T> |
| 72 | { |
| 73 | private S start; |
| 74 | |
| 75 | /** |
| 76 | * Constructs an iterable that simply delegates |
| 77 | * to the stepIterator() method. |
| 78 | */ |
| 79 | public StepIterable( S start ) |
| 80 | { |
| 81 | this.start = start; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * {@inheritDoc} |
| 86 | */ |
| 87 | public Iterator<T> iterator() |
| 88 | { |
| 89 | return stepIterator(start); |
| 90 | } |
| 91 | } |
| 92 | } |
| 93 | |