-
Notifications
You must be signed in to change notification settings - Fork 1
/
15298011985624.html
424 lines (263 loc) · 13.6 KB
/
15298011985624.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
<!doctype html>
<html class="no-js" lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>
Java中的十个"单行代码编程"(One Liner) - Junkman
</title>
<link href="atom.xml" rel="alternate" title="Junkman" type="application/atom+xml">
<link rel="stylesheet" href="asset/css/foundation.min.css" />
<link rel="stylesheet" href="asset/css/docs.css" />
<script src="asset/js/vendor/modernizr.js"></script>
<script src="asset/js/vendor/jquery.js"></script>
<script src="asset/highlightjs/highlight.pack.js"></script>
<link href="asset/highlightjs/styles/github.css" media="screen, projection" rel="stylesheet" type="text/css">
<script>hljs.initHighlightingOnLoad();</script>
<script type="text/javascript">
function before_search(){
var searchVal = 'site:panlw.github.io ' + document.getElementById('search_input').value;
document.getElementById('search_q').value = searchVal;
return true;
}
</script>
</head>
<body class="antialiased hide-extras">
<div class="marketing off-canvas-wrap" data-offcanvas>
<div class="inner-wrap">
<nav class="top-bar docs-bar hide-for-small" data-topbar>
<section class="top-bar-section">
<div class="row">
<div style="position: relative;width:100%;"><div style="position: absolute; width:100%;">
<ul id="main-menu" class="left">
<li id=""><a target="self" href="index.html">Home</a></li>
<li id=""><a target="_self" href="archives.html">Archives</a></li>
</ul>
<ul class="right" id="search-wrap">
<li>
<form target="_blank" onsubmit="return before_search();" action="http://google.com/search" method="get">
<input type="hidden" id="search_q" name="q" value="" />
<input tabindex="1" type="search" id="search_input" placeholder="Search"/>
</form>
</li>
</ul>
</div></div>
</div>
</section>
</nav>
<nav class="tab-bar show-for-small">
<a href="javascript:void(0)" class="left-off-canvas-toggle menu-icon">
<span> Junkman</span>
</a>
</nav>
<aside class="left-off-canvas-menu">
<ul class="off-canvas-list">
<li><a href="index.html">HOME</a></li>
<li><a href="archives.html">Archives</a></li>
<li><a href="about.html">ABOUT</a></li>
<li><label>Categories</label></li>
<li><a href="Infra.html">Infra</a></li>
<li><a href="Coding.html">Coding</a></li>
<li><a href="Modeling.html">Modeling</a></li>
<li><a href="Archtecting.html">Archtecting</a></li>
</ul>
</aside>
<a class="exit-off-canvas" href="#"></a>
<section id="main-content" role="main" class="scroll-container">
<script type="text/javascript">
$(function(){
$('#menu_item_index').addClass('is_active');
});
</script>
<div class="row">
<div class="large-8 medium-8 columns">
<div class="markdown-body article-wrap">
<div class="article">
<h1>Java中的十个"单行代码编程"(One Liner)</h1>
<div class="read-more clearfix">
<span class="date">2018/6/24</span>
<span>posted in </span>
<span class="posted-in"><a href='Java.html'>Java</a></span>
<span class="comments">
</span>
</div>
</div><!-- article -->
<div class="article-content">
<blockquote>
<p>译文: <a href="http://www.rowkey.me/blog/2017/09/09/java-oneliners/">http://www.rowkey.me/blog/2017/09/09/java-oneliners/</a><br/>
原文: <a href="https://github.com/aruld/java-oneliners/wiki">https://github.com/aruld/java-oneliners/wiki</a></p>
</blockquote>
<p>本文列举了十个使用一行代码即可独立完成 (不依赖其他代码) 的业务逻辑，主要依赖的是 Java8 中的 Lambda 和 Stream 等新特性以及 try-with-resources、JAXB 等。</p>
<ol>
<li><p>对列表 / 数组中的每个元素都乘以 2</p>
<pre><code class="language-java"> // Range是半开区间
int[] ia = range(1, 10).map(i -> i * 2).toArray();
List<Integer> result = range(1, 10).map(i -> i * 2).boxed().collect(toList());
</code></pre></li>
<li><p>计算集合 / 数组中的数字之和</p>
<pre><code class="language-java"> range(1, 1000).sum();
range(1, 1000).reduce(0, Integer::sum);
Stream.iterate(0, i -> i + 1).limit(1000).reduce(0, Integer::sum);
IntStream.iterate(0, i -> i + 1).limit(1000).reduce(0, Integer::sum);
</code></pre></li>
<li><p>验证字符串是否包含集合中的某一字符串</p>
<pre><code class="language-java">final List<String> keywords = Arrays.asList("brown", "fox", "dog", "pangram");
final String tweet = "The quick brown fox jumps over a lazy dog. #pangram http://www.rinkworks.com/words/pangrams.shtml";
keywords.stream().anyMatch(tweet::contains);
keywords.stream().reduce(false, (b, keyword) -> b || tweet.contains(keyword), (l, r) -> l || r);
</code></pre></li>
<li><p>读取文件内容</p>
<blockquote>
<p>原作者认为 try with resources 也是一种单行代码编程。</p>
</blockquote>
<pre><code class="language-java"> try (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
String fileText = reader.lines().reduce("", String::concat);
}
try (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
List<String> fileLines = reader.lines().collect(toCollection(LinkedList<String>::new));
}
try (Stream<String> lines = Files.lines(new File("data.txt").toPath(), Charset.defaultCharset())) {
List<String> fileLines = lines.collect(toCollection(LinkedList<String>::new));
}
</code></pre></li>
<li><p>输出歌曲《Happy Birthday to You!》 - 根据集合中不同的元素输出不同的字符串</p>
<pre><code class="language-java"> range(1, 5).boxed().map(i -> { out.print("Happy Birthday "); if (i == 3) return "dear NAME"; else return "to You"; }).forEach(out::println);
</code></pre></li>
<li><p>过滤并分组集合中的数字</p>
<pre><code class="language-java"> Map<String, List<Integer>> result = Stream.of(49, 58, 76, 82, 88, 90).collect(groupingBy(forPredicate(i -> i > 60, "passed", "failed")));
</code></pre></li>
<li><p>获取并解析 xml 协议的 Web Service</p>
<pre><code class="language-java">FeedType feed = JAXB.unmarshal(new URL("http://search.twitter.com/search.atom?&q=java8"), FeedType.class);
JAXB.marshal(feed, System.out);
</code></pre></li>
<li><p>获得集合中最小 / 最大的数字</p>
<pre><code class="language-java"> int min = Stream.of(14, 35, -7, 46, 98).reduce(Integer::min).get();
min = Stream.of(14, 35, -7, 46, 98).min(Integer::compare).get();
min = Stream.of(14, 35, -7, 46, 98).mapToInt(Integer::new).min();
int max = Stream.of(14, 35, -7, 46, 98).reduce(Integer::max).get();
max = Stream.of(14, 35, -7, 46, 98).max(Integer::compare).get();
max = Stream.of(14, 35, -7, 46, 98).mapToInt(Integer::new).max();
</code></pre></li>
<li><p>并行处理</p>
<pre><code class="language-java"> long result = dataList.parallelStream().mapToInt(line -> processItem(line)).sum();
</code></pre></li>
<li><p>集合上的各种查询 (LINQ in Java)</p>
<pre><code class="language-java">List<Album> albums = Arrays.asList(unapologetic, tailgates, red);
//筛选出至少有一个track评级4分以上的专辑，并按照名称排序后打印出来。
albums.stream()
.filter(a -> a.tracks.stream().anyMatch(t -> (t.rating >= 4)))
.sorted(comparing(album -> album.name))
.forEach(album -> System.out.println(album.name));
//合并所有专辑的track
List<Track> allTracks = albums.stream()
.flatMap(album -> album.tracks.stream())
.collect(toList());
//根据track的评分对所有track分组
Map<Integer, List<Track>> tracksByRating = allTracks.stream()
.collect(groupingBy(Track::getRating));
</code></pre></li>
</ol>
</div>
<div class="row">
<div class="large-6 columns">
<p class="text-left" style="padding:15px 0px;">
<a href="15299316548658.html"
title="Previous Post: hbase 的架构及设计">« hbase 的架构及设计</a>
</p>
</div>
<div class="large-6 columns">
<p class="text-right" style="padding:15px 0px;">
<a href="15295434052821.html"
title="Next Post: Open Sourcing Zuul 2">Open Sourcing Zuul 2 »</a>
</p>
</div>
</div>
<div class="comments-wrap">
<div class="share-comments">
<script type="text/javascript" src="//s7.addthis.com/js/300/addthis_widget.js#pubid=ra-5ae58078c0d7b2ab"></script>
</div>
</div>
</div><!-- article-wrap -->
</div><!-- large 8 -->
<div class="large-4 medium-4 columns">
<div class="hide-for-small">
<div id="sidebar" class="sidebar">
<div id="site-info" class="site-info">
<div class="site-a-logo"><img src="./asset/img/logo.jpg" /></div>
<h1>Junkman</h1>
<div class="site-des">“拾荒者”一词来自凯文・凯利的《失控》中关于机器学习的故事（“收集癖好机”如何完成他的收集工作）。</div>
<div class="social">
<a target="_blank" class="github" target="_blank" href="https://github.com/panlw/" title="GitHub">GitHub</a>
<a target="_blank" class="rss" href="atom.xml" title="RSS">RSS</a>
</div>
</div>
<div id="site-categories" class="side-item ">
<div class="side-header">
<h2>Categories</h2>
</div>
<div class="side-content">
<p class="cat-list">
<a href="Infra.html"><strong>Infra</strong></a>
<a href="Coding.html"><strong>Coding</strong></a>
<a href="Modeling.html"><strong>Modeling</strong></a>
<a href="Archtecting.html"><strong>Archtecting</strong></a>
</p>
</div>
</div>
<div id="site-categories" class="side-item">
<div class="side-header">
<h2>Recent Posts</h2>
</div>
<div class="side-content">
<ul class="posts-list">
<li class="post">
<a href="15517999043443.html">The Art of Crafting Architectural Diagrams</a>
</li>
<li class="post">
<a href="15517997955971.html">为什么说我们需要软件架构图？</a>
</li>
<li class="post">
<a href="15516128677869.html">DNS Servers That Offer Privacy and Filtering</a>
</li>
<li class="post">
<a href="15516123108194.html">Airbnb's Migration from Monolith to Services</a>
</li>
<li class="post">
<a href="15516097487470.html">Events As First-Class Citizens</a>
</li>
</ul>
</div>
</div>
</div><!-- sidebar -->
</div><!-- hide for small -->
</div><!-- large 4 -->
</div><!-- row -->
<div class="page-bottom clearfix">
<div class="row">
<p class="copyright">Copyright © 2015
Powered by <a target="_blank" href="http://www.mweb.im">MWeb</a>,
Theme used <a target="_blank" href="http://github.com">GitHub CSS</a>.</p>
</div>
</div>
</section>
</div>
</div>
<script src="asset/js/foundation.min.js"></script>
<script>
$(document).foundation();
function fixSidebarHeight(){
var w1 = $('.markdown-body').height();
var w2 = $('#sidebar').height();
if (w1 > w2) { $('#sidebar').height(w1); };
}
$(function(){
fixSidebarHeight();
})
$(window).load(function(){
fixSidebarHeight();
});
</script>
<script src="asset/chart/all-min.js"></script><script type="text/javascript">$(function(){ var mwebii=0; var mwebChartEleId = 'mweb-chart-ele-'; $('pre>code').each(function(){ mwebii++; var eleiid = mwebChartEleId+mwebii; if($(this).hasClass('language-sequence')){ var ele = $(this).addClass('nohighlight').parent(); $('<div id="'+eleiid+'"></div>').insertAfter(ele); ele.hide(); var diagram = Diagram.parse($(this).text()); diagram.drawSVG(eleiid,{theme: 'simple'}); }else if($(this).hasClass('language-flow')){ var ele = $(this).addClass('nohighlight').parent(); $('<div id="'+eleiid+'"></div>').insertAfter(ele); ele.hide(); var diagram = flowchart.parse($(this).text()); diagram.drawSVG(eleiid); } });});</script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script><script type="text/x-mathjax-config">MathJax.Hub.Config({TeX: { equationNumbers: { autoNumber: "AMS" } }});</script>
</body>
</html>