{"id":203043,"date":"2025-05-22T11:31:42","date_gmt":"2025-05-22T03:31:42","guid":{"rendered":"https:\/\/server.hk\/cnblog\/203043\/"},"modified":"2025-05-22T11:31:42","modified_gmt":"2025-05-22T03:31:42","slug":"java%e4%b8%ad%e5%87%bd%e6%95%b0%e5%8f%82%e6%95%b0%e7%9a%84%e9%80%86%e5%8f%98-covariance","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/203043\/","title":{"rendered":"Java\u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8 covariance"},"content":{"rendered":"

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

Java\u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8 covariance<\/h1>\n

\u4eca\u5929\u7ed9\u5927\u5bb6\u5e26\u6765\u4e86\u300aJava\u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8 covariance\u300b<\/span>\uff0c\u5176\u4e2d\u6d89\u53ca\u5230\u7684\u77e5\u8bc6\u70b9\u5305\u62ec<\/span>\u7b49\u7b49\uff0c\u65e0\u8bba\u4f60\u662f\u5c0f\u767d\u8fd8\u662f\u8001\u624b\uff0c\u90fd\u9002\u5408\u770b\u4e00\u770b\u54e6~\u6709\u597d\u7684\u5efa\u8bae\u4e5f\u6b22\u8fce\u5927\u5bb6\u5728\u8bc4\u8bba\u7559\u8a00\uff0c\u82e5\u662f\u770b\u5b8c\u6709\u6240\u6536\u83b7\uff0c\u4e5f\u5e0c\u671b\u5927\u5bb6\u80fd\u591a\u591a\u70b9\u8d5e\u652f\u6301\u5440\uff01\u4e00\u8d77\u52a0\u6cb9\u5b66\u4e60~<\/p>\n

Java \u4e2d\u51fd\u6570\u53c2\u6570\u9006\u53d8\uff1a\u5141\u8bb8\u51fd\u6570\u53c2\u6570\u58f0\u660e\u4e3a\u5176\u7236\u7c7b\u6216\u63a5\u53e3\uff0c\u65e0\u9700\u8f6c\u6362\u3002\u8d4b\u503c\u517c\u5bb9\u6027\u89c4\u5219\u5141\u8bb8\u5b50\u7c7b\u5bf9\u8c61\u5206\u914d\u7ed9\u7236\u7c7b\u5f15\u7528\u3002\u63d0\u9ad8\u4e86\u4ee3\u7801\u53ef\u91cd\u7528\u6027\uff0c\u5141\u8bb8\u51fd\u6570\u5904\u7406\u4e0d\u540c\u7c7b\u578b\u3002\u4fc3\u8fdb\u4e86\u826f\u597d\u7684\u9762\u5411\u5bf9\u8c61\u8bbe\u8ba1\uff0c\u5141\u8bb8\u4f7f\u7528\u7236\u7c7b\u5f15\u7528\u3002\u9006\u53d8\u4ec5\u9002\u7528\u4e8e\u51fd\u6570\u53c2\u6570\uff0c\u800c\u4e0d\u9002\u7528\u4e8e\u8fd4\u56de\u503c\u3002<\/p>\n

<\/p>\n

Java \u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8\uff08Covariance\uff09<\/h2>\n

\u5728 Java \u4e2d\uff0c\u9006\u53d8\u662f\u6307\u5141\u8bb8\u51fd\u6570\u53c2\u6570\u7c7b\u578b\u58f0\u660e\u4e3a\u5176\u7236\u7c7b\u6216\u63a5\u53e3\uff0c\u800c\u4e0d\u9700\u8981\u660e\u786e\u8f6c\u6362\u3002\u8fd9\u4e0e\u534f\u53d8\uff08Covariance\uff09\u76f8\u53cd\uff0c\u534f\u53d8\u5141\u8bb8\u51fd\u6570\u8fd4\u56de\u503c\u7c7b\u578b\u58f0\u660e\u4e3a\u5176\u5b50\u7c7b\u6216\u63a5\u53e3\u3002<\/p>\n

\u7406\u89e3\u9006\u53d8<\/h3>\n

\u8003\u8651\u4ee5\u4e0b\u51fd\u6570\uff1a<\/p>\n

public void print(Number n) {\n    System.out.println(n);\n}<\/pre>\n
\u8fd9\u4e2a\u51fd\u6570\u53ef\u4ee5\u63a5\u53d7 Number<\/code> \u53ca\u5176\u4efb\u4f55\u5b50\u7c7b\uff0c\u4f8b\u5982 Integer<\/code>\u3001Double<\/code> \u7b49\u3002\u8fd9\u662f\u56e0\u4e3a\u8d4b\u503c\u517c\u5bb9\u6027\u89c4\u5219\u5141\u8bb8\u4e00\u4e2a\u5b50\u7c7b\u5bf9\u8c61\u5206\u914d\u7ed9\u5176\u7236\u7c7b\u7684\u5f15\u7528\u3002<\/p>\n
\u5b9e\u6218\u6848\u4f8b<\/h3>\n
\u5047\u8bbe\u60a8\u6709\u4e00\u4e2a\u4fdd\u5b58 Integer<\/code> \u5143\u7d20\u7684 List<\/code>\uff1a<\/p>\n
List<Integer> integers = Arrays.asList(1, 2, 3);<\/pre>\n
\u73b0\u5728\uff0c\u4f60\u60f3\u5c06\u8fd9\u4e2a Integer<\/code> \u5217\u8868\u4f20\u9012\u7ed9\u4e00\u4e2a\u63a5\u53d7 Number<\/code> \u5217\u8868\u7684\u51fd\u6570\uff1a<\/p>\n
public void printNumbers(List<? super Number> numbers) {\n    for (Number n : numbers) {\n        System.out.println(n);\n    }\n}<\/pre>\n
\u7531\u4e8e\u5217\u8868\u7684\u7c7b\u578b\u4e3a <? super Number><\/code>\uff0c\u5b83\u53ef\u4ee5\u63a5\u53d7 Number<\/code> \u6216\u5176\u4efb\u4f55\u7236\u7c7b\u7684\u5217\u8868\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u4f20\u9012 integers<\/code> \u5217\u8868\u5230\u8be5\u51fd\u6570\uff1a<\/p>\n
printNumbers(integers);<\/pre>\n
\u4f18\u70b9<\/h3>\n
\u9006\u53d8\u7684\u4f18\u70b9\u5305\u62ec\uff1a<\/p>\n
    \n
  • \u63d0\u9ad8\u4e86\u4ee3\u7801\u7684\u53ef\u91cd\u7528\u6027\uff0c\u56e0\u4e3a\u5b83\u5141\u8bb8\u51fd\u6570\u5904\u7406\u4e0d\u540c\u7c7b\u578b\u800c\u65e0\u9700\u8fdb\u884c\u663e\u5f0f\u8f6c\u6362\u3002<\/li>\n
  • \u4fc3\u8fdb\u4e86\u826f\u597d\u7684\u9762\u5411\u5bf9\u8c61\u8bbe\u8ba1\uff0c\u56e0\u4e3a\u51fd\u6570\u53ef\u4ee5\u63a5\u53d7\u7236\u7c7b\u5f15\u7528\uff0c\u800c\u65e0\u9700\u4e86\u89e3\u5177\u4f53\u7684\u5b50\u7c7b\u7c7b\u578b\u3002<\/li>\n<\/ul>\n
    \u6ce8\u610f<\/h3>\n
    \u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u9006\u53d8\u4ec5\u9002\u7528\u4e8e\u51fd\u6570\u53c2\u6570\uff0c\u800c\u4e0d\u9002\u7528\u4e8e\u8fd4\u56de\u503c\u3002\u8fd9\u610f\u5473\u7740\u60a8\u4e0d\u80fd\u4f7f\u7528\u9006\u53d8\u6765\u8fd4\u56de\u5b50\u7c7b\u5bf9\u8c61\u800c\u58f0\u660e\u8fd4\u56de\u7c7b\u578b\u4e3a\u7236\u7c7b\u3002<\/p>\n
    \u7ec8\u4e8e\u4ecb\u7ecd\u5b8c\u5566\uff01\u5c0f\u4f19\u4f34\u4eec\uff0c\u8fd9\u7bc7\u5173\u4e8e\u300aJava\u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8 covariance\u300b\u7684\u4ecb\u7ecd\u5e94\u8be5\u8ba9\u4f60\u6536\u83b7\u591a\u591a\u4e86\u5427\uff01\u6b22\u8fce\u5927\u5bb6\u6536\u85cf\u6216\u5206\u4eab\u7ed9\u66f4\u591a\u9700\u8981\u5b66\u4e60\u7684\u670b\u53cb\u5427~\u516c\u4f17\u53f7\u4e5f\u4f1a\u53d1\u5e03\u6587\u7ae0\u76f8\u5173\u77e5\u8bc6\uff0c\u5feb\u6765\u5173\u6ce8\u5427\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
    Java\u4e2d\u51fd\u6570\u53c2\u6570\u7684\u9006\u53d8 cov...<\/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-203043","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/203043","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=203043"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/203043\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=203043"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=203043"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=203043"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}