transform.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head><meta http-equiv="content-type" content="text/html; charset=UTF-8" /><title>Transform xref</title><link type="text/css" rel="stylesheet" href="../../../../stylesheet.css" /></head><body><div id="overview"><a href="../../../../../apidocs/org/archive/crawler/util/Transform.html">View Javadoc</a></div><pre><a name="1" href="#1">1</a> <em class="comment">/*<em class="comment"> Transform</em></em><a name="2" href="#2">2</a> <em class="comment">*</em><a name="3" href="#3">3</a> <em class="comment">* $Id: Transform.java 4841 2007-01-06 06:51:07Z gojomo $</em><a name="4" href="#4">4</a> <em class="comment">*</em><a name="5" href="#5">5</a> <em class="comment">* Created on September 26, 2006</em><a name="6" href="#6">6</a> <em class="comment">*</em><a name="7" href="#7">7</a> <em class="comment">* Copyright (C) 2006 Internet Archive.</em><a name="8" href="#8">8</a> <em class="comment">*</em><a name="9" href="#9">9</a> <em class="comment">* This file is part of the Heritrix web crawler (crawler.archive.org).</em><a name="10" href="#10">10</a> <em class="comment">*</em><a name="11" href="#11">11</a> <em class="comment">* Heritrix is free software; you can redistribute it and/or modify</em><a name="12" href="#12">12</a> <em class="comment">* it under the terms of the GNU Lesser Public License as published by</em><a name="13" href="#13">13</a> <em class="comment">* the Free Software Foundation; either version 2.1 of the License, or</em><a name="14" href="#14">14</a> <em class="comment">* any later version.</em><a name="15" href="#15">15</a> <em class="comment">*</em><a name="16" href="#16">16</a> <em class="comment">* Heritrix is distributed in the hope that it will be useful,</em><a name="17" href="#17">17</a> <em class="comment">* but WITHOUT ANY WARRANTY; without even the implied warranty of</em><a name="18" href="#18">18</a> <em class="comment">* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</em><a name="19" href="#19">19</a> <em class="comment">* GNU Lesser Public License for more details.</em><a name="20" href="#20">20</a> <em class="comment">*</em><a name="21" href="#21">21</a> <em class="comment">* You should have received a copy of the GNU Lesser Public License</em><a name="22" href="#22">22</a> <em class="comment">* along with Heritrix; if not, write to the Free Software</em><a name="23" href="#23">23</a> <em class="comment">* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA</em><a name="24" href="#24">24</a> <em class="comment">*/</em><a name="25" href="#25">25</a> <strong>package</strong> <a href="../../../../org/archive/crawler/util/package-summary.html">org.archive.crawler.util</a>;<a name="26" href="#26">26</a> <a name="27" href="#27">27</a> <strong>import</strong> java.util.AbstractCollection;<a name="28" href="#28">28</a> <strong>import</strong> java.util.Collection;<a name="29" href="#29">29</a> <strong>import</strong> java.util.Iterator;<a name="30" href="#30">30</a> <a name="31" href="#31">31</a> <a name="32" href="#32">32</a> <em>/**<em>*</em></em><a name="33" href="#33">33</a> <em> * A transformation of a collection. The elements in the transform are based</em><a name="34" href="#34">34</a> <em> * on the elements of some other collection; the original collection's </em><a name="35" href="#35">35</a> <em> * elements are transformed using a specified transformer. Changes to the</em><a name="36" href="#36">36</a> <em> * original collection are automatically reflected in the transform and </em><a name="37" href="#37">37</a> <em> * vice-versa.</em><a name="38" href="#38">38</a> <em> * </em><a name="39" href="#39">39</a> <em> * <p>If the transformer returns null for a given original object, then that</em><a name="40" href="#40">40</a> <em> * object will not be included in the transform. Thus the transform might</em><a name="41" href="#41">41</a> <em> * be smaller than the original collection. Note that Transform instances</em><a name="42" href="#42">42</a> <em> * can never contain the null element.</em><a name="43" href="#43">43</a> <em> * </em><a name="44" href="#44">44</a> <em> * <p>This collection implementation does not support the optional add</em><a name="45" href="#45">45</a> <em> * operation.</em><a name="46" href="#46">46</a> <em> * </em><a name="47" href="#47">47</a> <em> * @author pjack</em><a name="48" href="#48">48</a> <em> *</em><a name="49" href="#49">49</a> <em> * @param <Original> the type of the original elements in the collection</em><a name="50" href="#50">50</a> <em> * @param <Transformed> the type of the tranformed elements</em><a name="51" href="#51">51</a> <em> */</em><a name="52" href="#52">52</a> <strong>public</strong> <strong>class</strong> Transform<Original,Transformed> <a name="53" href="#53">53</a> <strong>extends</strong> AbstractCollection<Transformed> {<a name="54" href="#54">54</a> <a name="55" href="#55">55</a> <em>/**<em>* The original collection. */</em></em><a name="56" href="#56">56</a> <strong>final</strong> <strong>private</strong> Collection<? <strong>extends</strong> Original> delegate;<a name="57" href="#57">57</a> <a name="58" href="#58">58</a> <em>/**<em>* Transforms the original objects. */</em></em><a name="59" href="#59">59</a> <strong>final</strong> <strong>private</strong> Transformer<Original,Transformed> transformer;<a name="60" href="#60">60</a> <a name="61" href="#61">61</a> <em>/**<em>*</em></em><a name="62" href="#62">62</a> <em> * Constructor.</em><a name="63" href="#63">63</a> <em> * </em><a name="64" href="#64">64</a> <em> * @param delegate The collection whose elements to transform.</em><a name="65" href="#65">65</a> <em> * @param transformer Transforms the elements</em><a name="66" href="#66">66</a> <em> */</em><a name="67" href="#67">67</a> <strong>public</strong> <a href="../../../../org/archive/crawler/util/Transform.html">Transform</a>(Collection<? <strong>extends</strong> Original> delegate, <a name="68" href="#68">68</a> Transformer<Original,Transformed> transformer) {<a name="69" href="#69">69</a> <strong>this</strong>.delegate = delegate;<a name="70" href="#70">70</a> <strong>this</strong>.transformer = transformer;<a name="71" href="#71">71</a> }<a name="72" href="#72">72</a> <a name="73" href="#73">73</a> <strong>public</strong> <strong>int</strong> size() {<a name="74" href="#74">74</a> <strong>int</strong> count = 0;<a name="75" href="#75">75</a> Iterator<Transformed> iter = iterator();<a name="76" href="#76">76</a> <strong>while</strong> (iter.hasNext()) {<a name="77" href="#77">77</a> iter.next();<a name="78" href="#78">78</a> count++;<a name="79" href="#79">79</a> }<a name="80" href="#80">80</a> <strong>return</strong> count;<a name="81" href="#81">81</a> }<a name="82" href="#82">82</a> <a name="83" href="#83">83</a> <strong>public</strong> Iterator<Transformed> iterator() {<a name="84" href="#84">84</a> <strong>return</strong> <strong>new</strong> TransformIterator<Original,Transformed>(<a name="85" href="#85">85</a> delegate.iterator(), transformer);<a name="86" href="#86">86</a> }<a name="87" href="#87">87</a> <a name="88" href="#88">88</a> <a name="89" href="#89">89</a> <em>/**<em>*</em></em><a name="90" href="#90">90</a> <em> * Returns a transform containing only objects of a given class.</em><a name="91" href="#91">91</a> <em> * </em><a name="92" href="#92">92</a> <em> * @param <Target> the target class</em><a name="93" href="#93">93</a> <em> * @param c the collection to transform</em><a name="94" href="#94">94</a> <em> * @param cls the class of objects to return </em><a name="95" href="#95">95</a> <em> * @return a collection containing only objects of class cls</em><a name="96" href="#96">96</a> <em> */</em><a name="97" href="#97">97</a> <strong>public</strong> <strong>static</strong> <Target> Collection<Target> subclasses(<a name="98" href="#98">98</a> Collection<? <strong>extends</strong> Object> c, <a name="99" href="#99">99</a> <strong>final</strong> Class<Target> cls) {<a name="100" href="#100">100</a> Transformer<Object,Target> t = <strong>new</strong> Transformer<Object,Target>() {<a name="101" href="#101">101</a> <strong>public</strong> Target transform(Object s) {<a name="102" href="#102">102</a> <strong>if</strong> (cls.isInstance(s)) {<a name="103" href="#103">103</a> <strong>return</strong> cls.<strong>cast</strong>(s);<a name="104" href="#104">104</a> } <strong>else</strong> {<a name="105" href="#105">105</a> <strong>return</strong> <strong>null</strong>;<a name="106" href="#106">106</a> }<a name="107" href="#107">107</a> }<a name="108" href="#108">108</a> };<a name="109" href="#109">109</a> <strong>return</strong> <strong>new</strong> Transform<Object,Target>(c, t);<a name="110" href="#110">110</a> }<a name="111" href="#111">111</a> }<a name="112" href="#112">112</a> <a name="113" href="#113">113</a> <a name="114" href="#114">114</a> <strong>class</strong> TransformIterator<Original,Transformed> implements Iterator<Transformed> {<a name="115" href="#115">115</a> <a name="116" href="#116">116</a> <strong>final</strong> <strong>private</strong> Iterator<? <strong>extends</strong> Original> iterator;<a name="117" href="#117">117</a> <strong>final</strong> <strong>private</strong> Transformer<Original,Transformed> transformer;<a name="118" href="#118">118</a> <strong>private</strong> Transformed next;<a name="119" href="#119">119</a> <a name="120" href="#120">120</a> <strong>public</strong> TransformIterator(Iterator<? <strong>extends</strong> Original> iterator, <a name="121" href="#121">121</a> Transformer<Original,Transformed> transformer) {<a name="122" href="#122">122</a> <strong>this</strong>.iterator = iterator;<a name="123" href="#123">123</a> <strong>this</strong>.transformer = transformer;<a name="124" href="#124">124</a> }<a name="125" href="#125">125</a> <a name="126" href="#126">126</a> <strong>public</strong> <strong>boolean</strong> hasNext() {<a name="127" href="#127">127</a> <strong>if</strong> (next != <strong>null</strong>) {<a name="128" href="#128">128</a> <strong>return</strong> <strong>true</strong>;<a name="129" href="#129">129</a> }<a name="130" href="#130">130</a> <strong>while</strong> (iterator.hasNext()) {<a name="131" href="#131">131</a> Original o = iterator.next();<a name="132" href="#132">132</a> next = transformer.transform(o);<a name="133" href="#133">133</a> <strong>if</strong> (next != <strong>null</strong>) { <a name="134" href="#134">134</a> <strong>return</strong> <strong>true</strong>;<a name="135" href="#135">135</a> }<a name="136" href="#136">136</a> }<a name="137" href="#137">137</a> <strong>return</strong> false;<a name="138" href="#138">138</a> }<a name="139" href="#139">139</a> <a name="140" href="#140">140</a> <strong>public</strong> Transformed next() {<a name="141" href="#141">141</a> <strong>if</strong> (!hasNext()) {<a name="142" href="#142">142</a> <strong>throw</strong> <strong>new</strong> IllegalStateException();<a name="143" href="#143">143</a> }<a name="144" href="#144">144</a> Transformed r = next;<a name="145" href="#145">145</a> next = <strong>null</strong>;<a name="146" href="#146">146</a> <strong>return</strong> r;<a name="147" href="#147">147</a> }<a name="148" href="#148">148</a> <a name="149" href="#149">149</a> <em class="comment">// FIXME: this can break standard Iterator contract, for example</em><a name="150" href="#150">150</a> <em class="comment">// transformIterator.next();</em><a name="151" href="#151">151</a> <em class="comment">// if(transformIterator.hasNext()) {</em><a name="152" href="#152">152</a> <em class="comment">// transformIterator.remove();</em><a name="153" href="#153">153</a> <em class="comment">// }</em><a name="154" href="#154">154</a> <em class="comment">// usual iterator contract is to remove the last object returned</em><a name="155" href="#155">155</a> <em class="comment">// by next; in this case the subsequent</em><a name="156" href="#156">156</a> <strong>public</strong> <strong>void</strong> remove() {<a name="157" href="#157">157</a> iterator.remove();<a name="158" href="#158">158</a> }<a name="159" href="#159">159</a> <a name="160" href="#160">160</a> }</pre><hr/><div id="footer">This page was automatically generated by <a href="http://maven.apache.org/">Maven</a></div></body></html>⌨️ 快捷键说明
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