{"rsdb":{"rid":"376851","subhead":"","postdate":"0","aid":"263782","fid":"90","uid":"1","topic":"1","content":"<div id=\"cnblogs_post_body\" class=\"blogpost-body cnblogs-markdown\"> \n <ul> \n  <li>\u63a5\u6536\u4e00\u5143\u51fd\u6570 \n   <ul> \n    <li><p><code>map<\/code> \u8f6c\u6362\u5143\u7d20\uff0c\u4e3b\u8981\u5e94\u7528\u4e8e\u4e0d\u53ef\u53d8\u96c6\u5408<\/p> <pre class=\"scala\"><code>(1 to 10).map(i =&gt; i * i)\n(1 to 10).flatMap(i =&gt; (1 to i).map(j =&gt; i * j))<\/code><\/pre><\/li> \n    <li><p><code>transform<\/code> \u4e0e <code>map<\/code> \u76f8\u540c\uff0c\u4e0d\u8fc7\u7528\u4e8e\u53ef\u53d8\u96c6\u5408\uff0c\u76f4\u63a5\u8f6c\u6362<\/p> <pre class=\"scala\"><code>ArrayBuffer(&quot;Peter&quot;, &quot;Paul&quot;, &quot;Mary&quot;).transform(_.toUpperCase)<\/code><\/pre><\/li> \n    <li><p><code>collect<\/code> \u63a5\u6536\u504f\u51fd\u6570(<code>PartialFunction<\/code>)\u4f5c\u4e3a\u53c2\u6570\uff1b\u6a21\u5f0f\u5339\u914d\u4e5f\u662f\u4e00\u79cd\u504f\u51fd\u6570<\/p> <pre class=\"scala\"><code>&quot;-3+4&quot;.collect {\n    case '+' =&gt; 1 ; \n    case '-' =&gt; -1 \n} \/\/ Vector(-1, 1)<\/code><\/pre><\/li> \n    <li><p><code>groupBy<\/code> \u6309\u6307\u5b9a\u51fd\u6570\u5206\u7ec4\uff0c\u8fd4\u56de <code>Map<\/code><\/p> <pre class=\"scala\"><code>val words = Array(&quot;Abc&quot;, &quot;ab&quot;)\nval map = words.groupBy(_.substring(0, 1).toUpperCase)\n\/\/ Map(A -&gt; Array(Abc, ab))<\/code><\/pre><\/li> \n   <\/ul><\/li> \n  <li>\u63a5\u6536\u4e8c\u5143\u51fd\u6570 \n   <ul> \n    <li><code>reduceLeft<\/code> \u4ece\u5de6\u5411\u53f3\u89c4\u7ea6 <code>f(f(f(a, b), c), d)<\/code><\/li> \n   <\/ul> <pre class=\"scala\"><code>  List(1, 7, 2, 9).reduceLeft(_ - _)\n  \/\/ ((1 - 7) - 2) - 9 = 1 - 7 - 2 - 9 = -17<\/code><\/pre> \n   <ul> \n    <li><p><code>reduceRight<\/code> \u4ece\u53f3\u5411\u5de6\u89c4\u7ea6 <code>f(a, f(b, f(c, d)))<\/code><\/p> <pre class=\"scala\"><code>List(1, 7, 2, 9).reduceRight(_ - _)\n\/\/ 1 - (7 - (2 - 9)) = 1 - 7 + 2 - 9 = -13<\/code><\/pre><\/li> \n    <li><code>foldLeft<\/code> \u63d0\u4f9b\u521d\u59cb\u503c+\u4e8c\u5143\u51fd\u6570\uff0c\u4ece\u5de6\u5411\u53f3\u6298\u53e0\uff0c\u6bcf\u6b21\u8ba1\u7b97\u7ed3\u679c\u5728\u5de6\u4fa7 \n     <ul> \n      <li>\u53ef\u7528 <code>\/:<\/code>\uff08\u8868\u793a\u6811\u5f62\u5de6\u4fa7\uff09\u64cd\u4f5c\u7b26\u8868\u793a\uff0c<code>(init \/: collection)(function)<\/code><\/li> \n     <\/ul><\/li> \n    <li><code>foldRight<\/code> \u63d0\u4f9b\u521d\u59cb\u503c+\u4e8c\u5143\u51fd\u6570\uff0c\u4ece\u53f3\u5411\u5de6\u6298\u53e0\uff0c\u6bcf\u6b21\u8ba1\u7b97\u7ed3\u679c\u5728\u53f3\u4fa7 \n     <ul> \n      <li>\u53ef\u7528 <code>:\\<\/code>\uff08\u8868\u793a\u6811\u5f62\u53f3\u4fa7\uff09\u64cd\u4f5c\u7b26\u8868\u793a\uff0c<code>(collection :\\ init)(function)<\/code><\/li> \n     <\/ul> <pre class=\"scala\"><code>List(1, 7, 2, 9).foldLeft(0)(_ - _)  \n(0 \/: List(1, 7, 2, 9))(_ - _)\n\/\/ 0 - 1 - 7 - 2 - 9 = -19<\/code><\/pre><\/li> \n    <li><p><code>scanLeft<\/code> \u548c <code>scanRight<\/code> \u7ed3\u5408\u4e86 folding \u548c mapping\uff0c\u7ed3\u679c\u4e3a\u6240\u6709\u7684\u4e2d\u95f4\u8fc7\u7a0b\u503c<\/p> <pre class=\"scala\"><code>(1 to 10).scanLeft(0)(_ + _) \/\/ Vector(0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55)<\/code><\/pre><\/li> \n   <\/ul><\/li> \n  <li><p><code>zip<\/code> \u62c9\u94fe\uff0c\u5373\u5c06\u4e24\u4e2a\u96c6\u5408\u5404\u4e2a\u5143\u7d20\u50cf\u62c9\u94fe\u4e00\u6837\u4ea4\u53c9\u7ed3\u5408\u5728\u4e00\u8d77<\/p> <pre class=\"scala\"><code>List(1,2,3) zip List(&quot;a&quot;,&quot;b&quot;,&quot;c&quot;) \/\/ List((1,a), (2,b), (3,c))<\/code><\/pre> \n   <ul> \n    <li>\u957f\u5ea6\u4e0d\u4e00\u81f4\u7684\u96c6\u5408\u5219\u4ee5\u8f83\u5c0f\u7684\u957f\u5ea6\u4e3a\u51c6<\/li> \n   <\/ul><\/li> \n  <li><p><code>zipAll<\/code> \u4e3a\u957f\u5ea6\u8f83\u77ed\u7684\u96c6\u5408\u8bbe\u7f6e\u9ed8\u8ba4\u503c\uff0c<\/p> <pre><code>this.zipAll(that, thisDefault, thatDefault)<\/code><\/pre><\/li> \n  <li><p><code>zipWithIndex<\/code> \u8fd4\u56de\u5143\u7d20\u53ca\u5bf9\u5e94\u7684\u4e0b\u6807<\/p> <pre class=\"scala\"><code>&quot;Scala&quot;.zipWithIndex\n\/\/  Vector((S,0), (c,1), (a,2), (l,3), (a,4))<\/code><\/pre><\/li> \n  <li><code>view<\/code> \u4e3a\u96c6\u5408\u521b\u5efa\u5ef6\u8fdf\u89c6\u56fe<br \/> <code>scala val lazyView = (1 to 1000000).view lazyView.take(100).last \/\/100<\/code> \n   <ul> \n    <li>\u5bf9\u89c6\u56fe\u7684\u64cd\u4f5c\u90fd\u4e0d\u4f1a\u7acb\u5373\u8ba1\u7b97\uff08\u5305\u62ec\u7b2c\u4e00\u4e2a\u5143\u7d20\u4e5f\u4e0d\u4f1a\uff09<\/li> \n    <li>\u4e0e <code>Stream<\/code> \u4e0d\u540c\uff0c\u4e0d\u4f1a\u7f13\u5b58\u4efb\u4f55\u503c<\/li> \n    <li><code>apply<\/code> \u65b9\u6cd5\u4f1a\u5f3a\u5236\u8ba1\u7b97\u6574\u4e2a\u89c6\u56fe\uff0c\u4f7f\u7528 <code>lazyView.take(i).last<\/code> \u4ee3\u66ff <code>lazyView(i)<\/code><\/li> \n   <\/ul><\/li> \n  <li><code>par<\/code> \u5e76\u884c\u5316\u96c6\u5408\uff0c\u540e\u7eed\u5e94\u7528\u7684\u65b9\u6cd5\u90fd\u4f1a\u5e76\u53d1\u8ba1\u7b97<br \/> <code>scala for (i &lt;- (0 until 100).par) print(s&quot; $i&quot;) \/\/ 1-99<\/code> \n   <ul> \n    <li>\u5f88\u597d\u7684\u89e3\u51b3\u5e76\u53d1\u7f16\u7a0b\u95ee\u9898<\/li> \n    <li>\u5c06\u96c6\u5408\u53d8\u4e3a\u5bf9\u4e8e\u7684\u5e76\u884c\u5316\u5b9e\u73b0<\/li> \n    <li>\u5bf9\u4e8e\u4ea7\u751f\u7684\u7ed3\u679c\uff0c\u4e0e\u4e32\u884c\u65b9\u5f0f\u7684\u7ed3\u679c\u4e00\u81f4 \uff08\u5982 <code>for...yield...<\/code>\uff09<\/li> \n    <li>\u53ef\u4f7f\u7528 <code>seq<\/code>\uff0c<code>toArray<\/code> \u7b49\u65b9\u6cd5\u5c06\u96c6\u5408\u8fd8\u539f<\/li> \n    <li>\u90e8\u5206\u65b9\u6cd5\u4e0d\u80fd\u5e76\u53d1\u64cd\u4f5c \n     <ul> \n      <li>\u4f7f\u7528 <code>reduce<\/code> \u66ff\u4ee3 <code>reduceLeft<\/code>\uff0c\u5148\u5bf9\u5404\u90e8\u5206\u96c6\u5408\u64cd\u4f5c\uff0c\u7136\u540e\u805a\u5408\u7ed3\u679c\uff0c\u4f46\u64cd\u4f5c\u5fc5\u987b\u6ee1\u8db3\u7ed3\u5408\u5f8b<\/li> \n      <li>\u4f7f\u7528 <code>aggregate<\/code> \u66ff\u4ee3 <code>foldLeft<\/code>\uff0c\u5148\u5bf9\u5404\u90e8\u5206\u96c6\u5408\u64cd\u4f5c\uff0c\u7136\u540e\u7528\u53e6\u4e00\u4e2a\u64cd\u4f5c\u5c06\u7ed3\u679c\u805a\u5408<\/li> \n     <\/ul> <code>str.par.aggregate(Set[Char]())(_ + _, _ ++ _) \/\/ \u7b49\u4ef7\u4e8e str.foldLeft(Set[Char]())(_ + _)<\/code><\/li> \n   <\/ul><\/li> \n <\/ul> \n<\/div>","orderid":"0","title":"Scala Collection Method","smalltitle":"","mid":"0","fname":"Scala","special_id":"0","bak_id":"0","info":"0","hits":"201","pages":"1","comments":"0","posttime":"2019-10-09 20:01:16","list":"1570622476","username":"admin","author":"","copyfrom":"","copyfromurl":"","titlecolor":"","fonttype":"0","titleicon":"0","picurl":"https:\/\/www.cppentry.com\/upload_files\/","ispic":"0","yz":"1","yzer":"","yztime":"0","levels":"0","levelstime":"0","keywords":"<A HREF='https:\/\/www.cppentry.com\/do\/search.php?type=keyword&keyword=Scala' target=_blank>Scala<\/A> <A HREF='https:\/\/www.cppentry.com\/do\/search.php?type=keyword&keyword=Collection' target=_blank>Collection<\/A> <A HREF='https:\/\/www.cppentry.com\/do\/search.php?type=keyword&keyword=Method' target=_blank>Method<\/A>","jumpurl":"","iframeurl":"","style":"","template":"a:3:{s:4:\"head\";s:0:\"\";s:4:\"foot\";s:0:\"\";s:8:\"bencandy\";s:0:\"\";}","target":"0","ip":"14.17.22.32","lastfid":"0","money":"0","buyuser":"","passwd":"","allowdown":"","allowview":"","editer":"","edittime":"0","begintime":"0","endtime":"0","description":"Scala Collection Method","lastview":"1713459520","digg_num":"0","digg_time":"0","forbidcomment":"0","ifvote":"0","heart":"","htmlname":"","city_id":"0"},"page":"1"}