{"id":202779,"date":"2025-05-22T11:30:37","date_gmt":"2025-05-22T03:30:37","guid":{"rendered":"https:\/\/server.hk\/cnblog\/202779\/"},"modified":"2025-05-22T11:30:37","modified_gmt":"2025-05-22T03:30:37","slug":"java-%e5%87%bd%e6%95%b0%e5%bc%8f%e7%bc%96%e7%a8%8b%e4%b8%ad%e7%9a%84-monad","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/202779\/","title":{"rendered":"Java \u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7684 monad"},"content":{"rendered":"

<\/b> <\/p>\n

Java \u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7684 monad<\/h1>\n

\u4e00\u5206\u8015\u8018\uff0c\u4e00\u5206\u6536\u83b7\uff01\u65e2\u7136\u90fd\u6253\u5f00\u8fd9\u7bc7\u300aJava \u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7684 monad\u300b<\/span>\uff0c\u5c31\u575a\u6301\u770b\u4e0b\u53bb\uff0c\u5b66\u4e0b\u53bb\u5427\uff01\u672c\u6587\u4e3b\u8981\u4f1a\u7ed9\u5927\u5bb6\u8bb2\u5230<\/span>\u7b49\u7b49\u77e5\u8bc6\u70b9\uff0c\u5982\u679c\u5927\u5bb6\u5bf9\u672c\u6587\u6709\u597d\u7684\u5efa\u8bae\u6216\u8005\u770b\u5230\u6709\u4e0d\u8db3\u4e4b\u5904\uff0c\u975e\u5e38\u6b22\u8fce\u5927\u5bb6\u79ef\u6781\u63d0\u51fa\uff01\u5728\u540e\u7eed\u6587\u7ae0\u6211\u4f1a\u7ee7\u7eed\u66f4\u65b0\u6587\u7ae0<\/span>\u76f8\u5173\u7684\u5185\u5bb9\uff0c\u5e0c\u671b\u5bf9\u5927\u5bb6\u90fd\u6709\u6240\u5e2e\u52a9\uff01<\/p>\n

Monad \u662f\u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7528\u4e8e\u5904\u7406\u53ef\u9009\u9879\u548c\u9519\u8bef\u7684\u7ed3\u6784\uff0c\u5305\u542b Functor \u548c Bind \u4e24\u4e2a\u90e8\u5206\u3002Functor \u5141\u8bb8\u5e94\u7528\u51fd\u6570\uff0cBind \u5141\u8bb8\u5c06\u5d4c\u5957 monad \u65e0\u7f1d\u8f6c\u6362\u4e3a\u5355\u4e00 monad\u3002Monad \u7684\u5b9e\u6218\u6848\u4f8b\u5305\u62ec\uff1aTry Monad\uff1a\u7528\u4e8e\u4ee5\u5b89\u5168\u7684\u65b9\u5f0f\u5904\u7406\u5f02\u5e38\u3002Either Monad\uff1a\u7528\u4e8e\u5904\u7406\u4e24\u4e2a\u9009\u9879\uff08\u5de6\u6216\u53f3\uff09\u3002Option Monad\uff1a\u7528\u4e8e\u5904\u7406\u7a7a\u503c\u3002<\/p>\n

<\/p>\n

Java \u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7684 Monad<\/strong><\/p>\n

\u7b80\u4ecb<\/strong><\/p>\n

Monad \u662f\u4e00\u79cd\u5728\u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7528\u4e8e\u5904\u7406\u53ef\u9009\u9879\u548c\u9519\u8bef\u7b49\u53ef\u9009\u7c7b\u578b\u7684\u6570\u636e\u7ed3\u6784\u3002\u5b83\u63d0\u4f9b\u4e86\u4e00\u79cd\u5b89\u5168\u4e14\u4f18\u96c5\u7684\u65b9\u5f0f\u6765\u7ec4\u5408\u548c\u53d8\u6362\u8fd9\u4e9b\u7c7b\u578b\uff0c\u800c\u4e0d\u4f1a\u4ea7\u751f NullPointerException \u6216\u5176\u4ed6\u9519\u8bef\u3002<\/p>\n

Monad \u7684\u57fa\u672c\u6982\u5ff5<\/strong><\/p>\n

Monad \u7531\u4e24\u4e2a\u90e8\u5206\u7ec4\u6210\uff1a<\/p>\n

    \n
  1. Functor<\/strong>\uff1a\u5141\u8bb8\u5e94\u7528\u51fd\u6570 f(x) \u2192 y<\/li>\n
  2. Bind (flatten)<\/strong>\uff1a\u5141\u8bb8\u5c06\u5d4c\u5957 monad\uff08a Monad<Monad<T>>\uff09\u65e0\u7f1d\u8f6c\u6362\u4e3a\u4e00\u4e2a\u5355\u4e00 monad\uff08a Monad<T>\uff09<\/li>\n<\/ol>\n

    \u5b9e\u6218\u6848\u4f8b<\/strong><\/p>\n

    Try Monad\uff08\u5904\u7406\u5f02\u5e38\uff09<\/strong><\/p>\n

    \u8bd5\u8bd5 Try monad\uff0c\u5b83\u7528\u4e8e\u4ee5\u5b89\u5168\u7684\u65b9\u5f0f\u5904\u7406\u5f02\u5e38\uff1a<\/p>\n

    \/\/ \u4f7f\u7528 Try.of() \u521b\u5efa\u5e26\u6709\u503c\u6216\u5f02\u5e38\u7684 Try \u5b9e\u4f8b\nTry<Integer> result = Try.of(() -> 1 \/ 0);\n\n\/\/ \u4f7f\u7528 isSuccess() \u68c0\u67e5\u662f\u5426\u6210\u529f\nif (result.isSuccess()) {\n  System.out.println(\"\u6210\u529f\uff1a\" + result.get());\n} else {\n  System.out.println(\"\u53d1\u751f\u5f02\u5e38\uff1a\" + result.getError());\n}<\/pre>\n
    Either Monad\uff08\u5904\u7406\u9009\u9879\uff09<\/strong><\/p>\n
    Either monad \u7528\u4e8e\u5904\u7406\u4e24\u4e2a\u9009\u9879\uff08\u5de6\u6216\u53f3\uff09\uff1a<\/p>\n
    \/\/ \u4f7f\u7528 Either.left() \u521b\u5efa\u4ee3\u8868\u5de6\u4fa7\u503c\u7684 Either \u5b9e\u4f8b\nEither<String, Integer> error = Either.left(\"\u9519\u8bef\u4fe1\u606f\");\n\n\/\/ \u4f7f\u7528 Either.right() \u521b\u5efa\u4ee3\u8868\u53f3\u4fa7\u503c\u7684 Either \u5b9e\u4f8b\nEither<String, Integer> success = Either.right(10);\n\n\/\/ \u6839\u636e\u4e0d\u540c\u7684\u60c5\u51b5\u91c7\u53d6\u884c\u52a8\nif (error.isLeft()) {\n  System.out.println(\"\u5de6\u4fa7\u503c\uff1a\" + error.getLeft());\n} else {\n  System.out.println(\"\u53f3\u4fa7\u503c\uff1a\" + success.getRight());\n}<\/pre>\n
    Option Monad\uff08\u5904\u7406\u7a7a\u503c\uff09<\/strong><\/p>\n
    Option monad \u7528\u4e8e\u5904\u7406\u7a7a\u503c\uff1a<\/p>\n
    \/\/ \u4f7f\u7528 Option.of() \u521b\u5efa\u5e26\u6709 Some(\u503c) \u6216 None \u7684 Option \u5b9e\u4f8b\nOption<String> name = Option.of(\"Alice\");\n\n\/\/ \u4f7f\u7528 isDefined() \u68c0\u67e5\u662f\u5426\u5b9a\u4e49\nif (name.isDefined()) {\n  System.out.println(\"\u5df2\u5b9a\u4e49\u503c\uff1a\" + name.get());\n} else {\n  System.out.println(\"\u65e0\u503c\");\n}<\/pre>\n
    \u4eca\u5929\u5e26\u5927\u5bb6\u4e86\u89e3\u4e86\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u5e0c\u671b\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\uff1b\u5173\u4e8e\u6587\u7ae0\u7684\u6280\u672f\u77e5\u8bc6\u6211\u4eec\u4f1a\u4e00\u70b9\u70b9\u6df1\u5165\u4ecb\u7ecd\uff0c\u6b22\u8fce\u5927\u5bb6\u5173\u6ce8\u516c\u4f17\u53f7\uff0c\u4e00\u8d77\u5b66\u4e60\u7f16\u7a0b~<\/p>\n","protected":false},"excerpt":{"rendered":"
    Java \u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7684 mon...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-202779","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/202779","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=202779"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/202779\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=202779"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=202779"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=202779"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}