{"id":4,"date":"2023-11-16T17:20:57","date_gmt":"2023-11-16T09:20:57","guid":{"rendered":"http:\/\/www.coffecat.cn\/?p=4"},"modified":"2023-11-28T08:37:15","modified_gmt":"2023-11-28T00:37:15","slug":"java8-stream%e6%b5%81%e4%b9%8b%e5%a4%9a%e5%ad%97%e6%ae%b5%e5%8e%bb%e9%87%8d","status":"publish","type":"post","link":"https:\/\/www.coffecat.cn\/index.php\/2023\/11\/16\/java8-stream%e6%b5%81%e4%b9%8b%e5%a4%9a%e5%ad%97%e6%ae%b5%e5%8e%bb%e9%87%8d\/","title":{"rendered":"Java8 Stream\u6d41\u4e4b\u591a\u5b57\u6bb5\u53bb\u91cd"},"content":{"rendered":"\n<p>\u6700\u8fd1\u6709\u4e00\u4e2a\u9700\u6c42\uff0c\u9700\u8981\u5728\u505a\u591a\u8868\u5173\u8054\u67e5\u8be2\u7684\u540c\u65f6\u4f7f\u7528\u5176\u4e2d\u67d0\u4e00\u4e2a\u8868\u4e2d\u7684\u4e24\u4e2a\u5b57\u6bb5\u8fdb\u884c\u53bb\u91cd\uff0c\u4e4d\u4e00\u542c\u662f\u6ca1\u6709\u95ee\u9898\u7684\uff0c\u7b2c\u4e00\u53cd\u5e94\u662f\u4f7f\u7528DISTINCT\u51fd\u6570\u8fdb\u884c\u53bb\u91cd\uff0c\u5f53\u4f7f\u7528\u65f6\u5374\u53d1\u73b0\uff0cDISTINCT\u51fd\u6570\u5b9a\u4e49\u5728\u7b2c\u4e00\u4e2a\u5f00\u59cb\u7684\u5b57\u6bb5\uff08\u5373select\u540e\u5f00\u59cb\u7684\u7b2c\u4e00\u4e2a\u5b57\u6bb5\uff09\uff0c\u5982\u679c\u7528\u5728\u5176\u4ed6\u4f4d\u7f6e\u4f1a\u62a5\u3010\u7f3a\u5931\u8868\u8fbe\u5f0f\u3011\uff0c\u5728\u6211\u7684\u4e2a\u4e1a\u52a1\u903b\u8f91\u4e2d\u662f\u4e0d\u6ee1\u8db3\u7684\uff08\u56e0\u4e3a\u6211\u9700\u8981\u67e5\u8be2\u5176\u4ed6\u5b57\u6bb5\u7684\u540c\u65f6\u6839\u636e\u67d0\u4e24\u4e2a\u5b57\u6bb5\u8fdb\u884c\u53bb\u91cd\uff09\uff0c\u5f53\u5373\u95ee\u4e86\u5ea6\u5a18\uff0c\u7ed9\u7684\u63d0\u793a\u662f\u4f7f\u7528GROUP BY\u5206\u7ec4\u51fd\u6570\u8fdb\u884c\u5206\u7ec4\uff0c\u4f46\u662f\u6211\u662f\u4f7f\u7528\u7684oracle\u6570\u636e\u5e93\uff0c\u5982\u679c\u4f7f\u7528GROUP BY\u5206\u7ec4\u51fd\u6570\u7684\u8bdd\u5c31\u5fc5\u987b\u4f7f\u7528COUNT\u51fd\u6570\u5bf9\u6240\u6709\u975eCOUNT\u5217\u8fdb\u884cGROUP BY\uff0c\u4f46\u663e\u7136\u4e5f\u4e0d\u6ee1\u8db3\u4e1a\u52a1\u9700\u6c42\uff0c\u9700\u8981\u6267\u884c\u7684sql\u4e2d\u6ca1\u6709\u9700\u8981COUNT\u7684\u5217\u3002\u540e\u6765\u53c8\u95ee\u4e86chatGPT\uff0c\u7ed9\u51fa\u7684\u65b9\u6848\u662f\u53ef\u4ee5\u901a\u8fc7\u7a97\u53e3\u51fd\u6570ROW_NUMBER()\u548cPARTITION BY\u6765\u8fdb\u884c\u53bb\u91cd\uff0c\u4f46\u5f97\u51fa\u7684\u7ed3\u679c\u548c\u4f7f\u7528\u4e0a\u9762\u4e24\u79cd\u7c7b\u4f3c\uff0c\u65e0\u6cd5\u5728\u7ed9\u5b9a\u67e5\u8be2\u591a\u4e2a\u5b57\u6bb5\u7684\u540c\u65f6\u5bf9\u5176\u4e2d\u7684\u4e24\u4e2a\u5b57\u6bb5\u8fdb\u884c\u53bb\u91cd\u4e14\u5b9e\u73b0\u8d77\u6765\u4e5f\u76f8\u5bf9\u524d\u4e24\u79cd\u590d\u6742\uff08\u5176\u5b9e\u662f\u81ea\u5df1\u4e4b\u524d\u7528\u7a97\u53e3\u51fd\u6570\u6bd4\u8f83\u5c11\uff09\uff0c\u4e8e\u662f\u5f53\u5373\u95ee\u4e86\u4e1a\u52a1\u8fd9\u4e2a\u9700\u6c42\u5b9e\u73b0\u65b9\u6848\u662f\u8c01\u63d0\u4f9b\u7684\uff0c\u4ece\u4e1a\u52a1\u90a3\u91cc\u5f97\u77e5\u53e6\u5916\u4e00\u4f4d\u5f00\u53d1\u5c0f\u4f19\u4f34\u5df2\u7ecf\u5b9e\u73b0\u4e86\u8fd9\u4e2a\u529f\u80fd\uff08\u5fc3\u60f3\uff0c\u4e0d\u4f1a\u662f\u5199\u4e86\u4e00\u4e2a\u5de8\u590d\u6742\u7684sql\u5427\uff09\uff0c\u7ed3\u679c\u548c\u5fc3\u91cc\u60f3\u7684\u7c7b\u4f3c\uff0c\u662f\u901a\u8fc7\u4ee3\u7801\u8fdb\u884c\u8fc7\u6ee4\u7684\uff0c\u867d\u7136\u4f1a\u6709\u4e00\u4e22\u4e22\u7684\u6027\u80fd\u95ee\u9898\uff0c\u4f46\u662f\u80fd\u5b9e\u73b0\u5c31\u53ef\u4ee5\u5ffd\u7565\u4e0d\u8bb0\uff08\u8fd9\u91cc\u662f\u60f3\u8bf4\uff0c\u5f53\u4f7f\u7528\u4ee3\u7801\u8fc7\u6ee4\u7684\u524d\u63d0\u662f\u5c06\u6570\u636e\u67e5\u8be2\u51fa\u6765\uff0c\u90a3\u4e48\u67e5\u8be2\u51fa\u6765\u7684\u6570\u636e\u80af\u5b9a\u8981\u6bd4\u8fc7\u6ee4\u540e\u7684\u6570\u636e\u591a\uff0c\u5982\u679c\u6570\u636e\u91cf\u4e0d\u5927\u7684\u60c5\u51b5\u4e0b\u5176\u5b9e\u6027\u80fd\u95ee\u9898\u53ef\u4ee5\u5ffd\u7565\uff0c\u4f46\u662f\u5982\u679c\u6570\u636e\u91cf\u8f83\u5927\u7684\u60c5\u51b5\u5176\u5b9e\u67e5\u8be2\u4e0a\u8fd8\u662f\u4f1a\u6709\u4f18\u5316\u7684\u7a7a\u95f4\uff09<\/p>\n\n\n\n<p>\u6211\u770b\u4e86\u4e00\u4e0b\u5f00\u53d1\u5c0f\u4f19\u4f34\u7684\u4ee3\u7801\uff0c\u53d1\u73b0\u662f\u4f7f\u7528\u4e86\u6d41\u7684\u65b9\u5f0f\u8fdb\u884c\u8fc7\u6ee4\u53bb\u91cd<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"java\" class=\"language-java\"><code>list.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -&gt; new TreeSet&lt;&gt;(Comparator.comparing(o -&gt; o.getUserName() + \";\" + o.getPassWord()))), ArrayList::new));<\/code><\/code><\/pre>\n\n\n\n<p>\u4f7f\u7528\u6d41\u7684\u96c6\u5408<code>collect<\/code>\u65b9\u6cd5\uff0c\u4ee5\u53ca<code>TreeSet<\/code>\u548c\u9ed8\u8ba4\u6392\u5e8f\u65b9\u6cd5\u8fdb\u884c\u51fd\u6570\u5f0f\u7f16\u7a0b\uff0c\u7531\u4e8e\u5728\u4e00\u4e2a\u6d41\u4e2d\uff0c\u53ef\u4ee5\u8fde\u5f88\u957f\u3002\u901a\u8fc7 Collectors.toCollection \u65b9\u6cd5\u521b\u5efa\u4e86\u4e00\u4e2a TreeSet \u5b9e\u4f8b\uff0c\u5e76\u5c06\u5176\u4f20\u9012\u7ed9\u4e86 collectingAndThen \u65b9\u6cd5\u3002\u7531\u4e8e\u6ca1\u6709\u63d0\u4f9b\u6bd4\u8f83\u5668\uff08Comparator\uff09\uff0cTreeSet \u5c06\u4f7f\u7528\u5143\u7d20\u7684\u81ea\u7136\u987a\u5e8f\u8fdb\u884c\u6392\u5e8f\u3002\u5c06\u5217\u8868\u4e2d\u7684\u5143\u7d20\u6536\u96c6\u5230\u4e00\u4e2a\u6309\u7167\u81ea\u7136\u987a\u5e8f\u6392\u5e8f\u7684 TreeSet \u4e2d\uff0c\u5e76\u5c06 TreeSet \u4f5c\u4e3a\u6700\u7ec8\u7684\u7ed3\u679c\u8fd4\u56de\u3002<\/p>\n\n\n\n<p>\u4e5f\u53ef\u4ee5\u7528\u53e6\u5916\u4e00\u79cd\u65b9\u5f0f\uff0c\u53bb\u91cd\u7684\u5b57\u6bb5\u53ef\u4ee5\u662f\u4e00\u4e2a\u4e5f\u53ef\u4ee5\u662f\u591a\u4e2a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"java\" class=\"language-java\">list.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(\n() -&gt; new TreeSet&lt;&gt;(Comparator.comparing(User::getUserName).thenComparing(User::getPassWord))\n), ArrayList&lt;SurvivalMonitor&gt;::new));<\/code><\/pre>\n\n\n\n<p>\u901a\u8fc7\u8fd9\u6837\u83b7\u53d6\u7684\u96c6\u5408\u5c31\u662f\u4f7f\u7528\u76f8\u5173\u5b57\u6bb5\u8fdb\u884c\u53bb\u91cd\u540e\u7684\u96c6\u5408\u4e86\uff0c\u4e4b\u524d\u5728\u7528\u6d41\u7684\u65f6\u5019\u5f88\u5c11\u505a\u8fd9\u6837\u5f88\u957f\u7684\u94fe\u5f0f\u7f16\u7a0b\uff0c\u540c\u65f6collect\u65b9\u6cd5\u4e5f\u662f\u5355\u72ec\u4f7f\u7528\u7684\u5c45\u591a\uff0c\u6211\u67e5\u4e86\u4e00\u4e0b\u6574\u4e2a\u670d\u52a1\u4e2d\u53ea\u6709\u4e00\u5904\u4f7f\u7528\u4e86\u8fd9\u79cd\u65b9\u5f0f\uff0c\u5b66\u4e60\u5230\u4e86\u4e00\u79cd\u6ca1\u6709\u78b0\u5230\u7684\u65b0\u65b9\u6cd5\uff0c\u540e\u9762\u6216\u591a\u6216\u5c11\u4f1a\u7528\u5230\uff0c\u6240\u4ee5\u5728\u8fd9\u91cc\u5148\u8bb0\u5f55\u4e00\u4e0b<\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6700\u8fd1\u6709\u4e00\u4e2a\u9700\u6c42\uff0c\u9700\u8981\u5728\u505a\u591a\u8868\u5173\u8054\u67e5\u8be2\u7684\u540c\u65f6\u4f7f\u7528\u5176\u4e2d\u67d0\u4e00\u4e2a\u8868\u4e2d\u7684\u4e24\u4e2a\u5b57\u6bb5\u8fdb\u884c\u53bb\u91cd\uff0c\u4e4d\u4e00\u542c\u662f\u6ca1\u6709\u95ee\u9898\u7684\uff0c\u7b2c\u4e00\u53cd\u5e94\u662f &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/www.coffecat.cn\/index.php\/2023\/11\/16\/java8-stream%e6%b5%81%e4%b9%8b%e5%a4%9a%e5%ad%97%e6%ae%b5%e5%8e%bb%e9%87%8d\/\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201cJava8 Stream\u6d41\u4e4b\u591a\u5b57\u6bb5\u53bb\u91cd\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":["post-4","post","type-post","status-publish","format-standard","hentry","category-scatteredtechnicalpoints"],"views":1088,"_links":{"self":[{"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/posts\/4","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/comments?post=4"}],"version-history":[{"count":29,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/posts\/4\/revisions"}],"predecessor-version":[{"id":147,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/posts\/4\/revisions\/147"}],"wp:attachment":[{"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/media?parent=4"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/categories?post=4"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.coffecat.cn\/index.php\/wp-json\/wp\/v2\/tags?post=4"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}