{"id":450,"date":"2005-08-10T06:36:26","date_gmt":"2005-08-10T06:36:26","guid":{"rendered":"http:\/\/davidhuangyidong.wordpress.com\/2005\/08\/10\/java-v-0-001-upcasting"},"modified":"2005-08-10T06:36:26","modified_gmt":"2005-08-10T06:36:26","slug":"java-v-0-001-upcasting","status":"publish","type":"post","link":"https:\/\/blog.huangyidong.com\/?p=450","title":{"rendered":"Java V 0.001&#8212;&#8212;Upcasting"},"content":{"rendered":"<div id=\"msgcns!486FBE8B011CEB7D!578\" class=\"bvMsg\">\n<div align=\"center\"><strong><font color=\"#00ff00\">====Upcasting====<\/font><\/strong><\/div>\n<div>\u00a0<\/div>\n<div>\u5047\u8bbe\u6211\u4eec\u7528Java\u5199\u4e86\u8fd9\u6837\u4e00\u4e2a\u51fd\u6570\uff1a<\/div>\n<div>\u00a0<\/div>\n<div><font color=\"#ffff00\">void doStuff(Shape s) &#123;<br \/>\u00a0 s.erase();<br \/>\u00a0 \/\/ &#8230;<br \/>\u00a0 s.draw();<br \/>&#125;<\/font><\/div>\n<div>\u00a0<\/div>\n<div>\u8fd9\u4e2a\u51fd\u6570\u53ef\u4e0e\u4efb\u4f55\u201c\u51e0\u4f55\u5f62\u72b6\u201d\uff08Shape\uff09\u901a\u4fe1\uff0c\u6240\u4ee5\u5b8c\u5168\u72ec\u7acb\u4e8e\u5b83\u8981\u63cf\u7ed8\uff08draw\uff09\u548c\u5220\u9664\uff08erase\uff09\u7684\u4efb\u4f55\u7279\u5b9a\u7c7b\u578b\u7684\u5bf9\u8c61\u3002\u5982\u679c\u6211\u4eec\u5728\u5176\u4ed6\u4e00\u4e9b\u7a0b\u5e8f\u91cc\u4f7f\u7528doStuff()\u51fd\u6570\uff1a<\/div>\n<div>\u00a0<\/div>\n<div>\u00a0<\/div>\n<div><font>Circle c = new Circle();<br \/>Triangle t = new Triangle();<br \/>Line l = new Line();<br \/>doStuff(c);<br \/>doStuff(t);<br \/>doStuff(l);<\/font><\/div>\n<div>\u00a0<\/div>\n<div>\u00a0<\/div>\n<div>\u90a3\u4e48\u5bf9doStuff()\u7684\u8c03\u7528\u4f1a\u81ea\u52a8\u826f\u597d\u5730\u5de5\u4f5c\uff0c\u65e0\u8bba\u5bf9\u8c61\u7684\u5177\u4f53\u7c7b\u578b\u662f\u4ec0\u4e48\u3002<br \/>\u8fd9\u5b9e\u9645\u662f\u4e00\u4e2a\u975e\u5e38\u6709\u7528\u7684\u7f16\u7a0b\u6280\u5de7\u3002\u8bf7\u8003\u8651\u4e0b\u9762\u8fd9\u884c\u4ee3\u7801\uff1a<\/div>\n<div>doStuff(c);<\/div>\n<div>\u6b64\u65f6\uff0c\u4e00\u4e2aCircle\uff08\u5706\uff09\u53e5\u67c4\u4f20\u9012\u7ed9\u4e00\u4e2a\u672c\u6765\u671f\u5f85Shape\uff08\u5f62\u72b6\uff09\u53e5\u67c4\u7684\u51fd\u6570\u3002\u7531\u4e8e\u5706\u662f\u4e00\u79cd\u51e0\u4f55\u5f62\u72b6\uff0c\u6240\u4ee5doStuff()\u80fd\u6b63\u786e\u5730\u8fdb\u884c\u5904\u7406\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c<font color=\"#ff0000\">\u51e1\u662fdoStuff()\u80fd\u53d1\u7ed9\u4e00\u4e2aShape\u7684\u6d88\u606f\uff0cCircle\u4e5f\u80fd\u63a5\u6536\u3002\u6240\u4ee5\u8fd9\u6837\u505a\u662f\u5b89\u5168\u7684\uff0c\u4e0d\u4f1a\u9020\u6210\u9519\u8bef\u3002<\/font><\/div>\n<div><font color=\"#00ff00\">\u6211\u4eec\u5c06\u8fd9\u79cd\u628a\u884d\u751f\u7c7b\u578b\u5f53\u4f5c\u5b83\u7684\u57fa\u672c\u7c7b\u578b\u5904\u7406\u7684\u8fc7\u7a0b\u53eb\u4f5c\u201cUpcasting\u201d\uff08\u4e0a\u6eaf\u9020\u578b\uff09<\/font>\u5176\u4e2d\uff0c\u201ccast\u201d\uff08\u9020\u578b\uff09\u662f\u6307\u6839\u636e\u4e00\u4e2a\u73b0\u6210\u7684\u6a21\u578b\u521b\u5efa\uff1b\u800c\u201cUp\u201d\uff08\u5411\u4e0a\uff09\u8868\u660e\u7ee7\u627f\u7684\u65b9\u5411\u662f\u4ece\u201c\u4e0a\u9762\u201d\u6765\u7684\u2014\u2014\u5373\u57fa\u7840\u7c7b\u4f4d\u4e8e\u9876\u90e8\uff0c\u800c\u884d\u751f\u7c7b\u5728\u4e0b\u65b9\u5c55\u5f00\u3002\u6240\u4ee5\uff0c\u6839\u636e\u57fa\u7840\u7c7b\u8fdb\u884c\u9020\u578b\u5c31\u662f\u4e00\u4e2a\u4ece\u4e0a\u9762\u7ee7\u627f\u7684\u8fc7\u7a0b\uff0c\u5373\u201cUpcasting\u201d\u3002<br \/><font color=\"#ff0000\"><\/font><\/div>\n<div><font color=\"#ff0000\">\u5728\u9762\u5411\u5bf9\u8c61\u7684\u7a0b\u5e8f\u91cc\uff0c\u901a\u5e38\u90fd\u8981\u7528\u5230\u4e0a\u6eaf\u9020\u578b\u6280\u672f\u3002\u8fd9\u662f\u907f\u514d\u53bb\u8c03\u67e5\u51c6\u786e\u7c7b\u578b\u7684\u4e00\u4e2a\u597d\u529e\u6cd5<\/font><\/div>\n<div>\u8bf7\u770b\u770bdoStuff()\u91cc\u7684\u4ee3\u7801\uff1a<\/div>\n<div>s.erase();<br \/>\/\/ &#8230;<br \/>s.draw();<\/div>\n<div>\u00a0<\/div>\n<div>\u6ce8\u610f\u5b83\u5e76\u672a\u8fd9\u6837\u8868\u8fbe\uff1a\u201c\u5982\u679c\u4f60\u662f\u4e00\u4e2aCircle\uff0c\u5c31\u8fd9\u6837\u505a\uff1b\u5982\u679c\u4f60\u662f\u4e00\u4e2aSquare\uff0c\u5c31\u90a3\u6837\u505a\uff1b\u7b49\u7b49\u201d\u3002\u82e5\u90a3\u6837\u7f16\u5199\u4ee3\u7801\uff0c\u5c31\u9700\u68c0\u67e5\u4e00\u4e2aShape\u6240\u6709\u53ef\u80fd\u7684\u7c7b\u578b\uff0c\u5982\u5706\u3001\u77e9\u5f62\u7b49\u7b49\u3002\u8fd9\u663e\u7136\u662f\u975e\u5e38\u9ebb\u70e6\u7684\uff0c\u800c\u4e14\u6bcf\u6b21\u6dfb\u52a0\u4e86\u4e00\u79cd\u65b0\u7684Shape\u7c7b\u578b\u540e\uff0c\u90fd\u8981\u76f8\u5e94\u5730\u8fdb\u884c\u4fee\u6539\u3002\u5728\u8fd9\u513f\uff0c\u6211\u4eec\u53ea\u9700\u8bf4\uff1a\u201c\u4f60\u662f\u4e00\u79cd\u51e0\u4f55\u5f62\u72b6\uff0c\u6211\u77e5\u9053\u4f60\u80fd\u5c06\u81ea\u5df1\u5220\u6389\uff0c\u5373erase()\uff1b\u8bf7\u81ea\u5df1\u91c7\u53d6\u90a3\u4e2a\u884c\u52a8\uff0c\u5e76\u81ea\u5df1\u53bb\u63a7\u5236\u6240\u6709\u7684\u7ec6\u8282\u5427\u3002\u201d<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>====Upcasting==== \u00a0 \u5047\u8bbe\u6211\u4eec\u7528Java\u5199\u4e86\u8fd9\u6837\u4e00\u4e2a\u51fd\u6570\uff1a \u00a0 void doStuff(Shape s) &#123;\u00a0 s.erase();\u00a0 \/\/ &#8230;\u00a0 s.draw();&#125; \u00a0 \u8fd9\u4e2a\u51fd\u6570\u53ef\u4e0e\u4efb\u4f55\u201c\u51e0\u4f55\u5f62\u72b6\u201d\uff08Shape\uff09\u901a\u4fe1\uff0c\u6240\u4ee5\u5b8c\u5168\u72ec\u7acb\u4e8e\u5b83\u8981\u63cf\u7ed8\uff08draw\uff09\u548c\u5220\u9664\uff08erase\uff09\u7684\u4efb\u4f55\u7279\u5b9a\u7c7b\u578b\u7684\u5bf9\u8c61\u3002\u5982\u679c\u6211\u4eec\u5728\u5176\u4ed6\u4e00\u4e9b\u7a0b\u5e8f\u91cc\u4f7f\u7528doStuff()\u51fd\u6570\uff1a \u00a0 \u00a0 Circle c = new Circle();Triangle t = new Triangle();Line l = new Line();doStuff(c);doStuff(t);doStuff(l); \u00a0 \u00a0 \u90a3\u4e48\u5bf9doStuff()\u7684\u8c03\u7528\u4f1a\u81ea\u52a8\u826f\u597d\u5730\u5de5\u4f5c\uff0c\u65e0\u8bba\u5bf9\u8c61\u7684\u5177\u4f53\u7c7b\u578b\u662f\u4ec0\u4e48\u3002\u8fd9\u5b9e\u9645\u662f\u4e00\u4e2a\u975e\u5e38\u6709\u7528\u7684\u7f16\u7a0b\u6280\u5de7\u3002\u8bf7\u8003\u8651\u4e0b\u9762\u8fd9\u884c\u4ee3\u7801\uff1a doStuff(c); \u6b64\u65f6\uff0c\u4e00\u4e2aCircle\uff08\u5706\uff09\u53e5\u67c4\u4f20\u9012\u7ed9\u4e00\u4e2a\u672c\u6765\u671f\u5f85Shape\uff08\u5f62\u72b6\uff09\u53e5\u67c4\u7684\u51fd\u6570\u3002\u7531\u4e8e\u5706\u662f\u4e00\u79cd\u51e0\u4f55\u5f62\u72b6\uff0c\u6240\u4ee5doStuff()\u80fd\u6b63\u786e\u5730\u8fdb\u884c\u5904\u7406\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u51e1\u662fdoStuff()\u80fd\u53d1\u7ed9\u4e00\u4e2aShape\u7684\u6d88\u606f\uff0cCircle\u4e5f\u80fd\u63a5\u6536\u3002\u6240\u4ee5\u8fd9\u6837\u505a\u662f\u5b89\u5168\u7684\uff0c\u4e0d\u4f1a\u9020\u6210\u9519\u8bef\u3002 \u6211\u4eec\u5c06\u8fd9\u79cd\u628a\u884d\u751f\u7c7b\u578b\u5f53\u4f5c\u5b83\u7684\u57fa\u672c\u7c7b\u578b\u5904\u7406\u7684\u8fc7\u7a0b\u53eb\u4f5c\u201cUpcasting\u201d\uff08\u4e0a\u6eaf\u9020\u578b\uff09\u5176\u4e2d\uff0c\u201ccast\u201d\uff08\u9020\u578b\uff09\u662f\u6307\u6839\u636e\u4e00\u4e2a\u73b0\u6210\u7684\u6a21\u578b\u521b\u5efa\uff1b\u800c\u201cUp\u201d\uff08\u5411\u4e0a\uff09\u8868\u660e\u7ee7\u627f\u7684\u65b9\u5411\u662f\u4ece\u201c\u4e0a\u9762\u201d\u6765\u7684\u2014\u2014\u5373\u57fa\u7840\u7c7b\u4f4d\u4e8e\u9876\u90e8\uff0c\u800c\u884d\u751f\u7c7b\u5728\u4e0b\u65b9\u5c55\u5f00\u3002\u6240\u4ee5\uff0c\u6839\u636e\u57fa\u7840\u7c7b\u8fdb\u884c\u9020\u578b\u5c31\u662f\u4e00\u4e2a\u4ece\u4e0a\u9762\u7ee7\u627f\u7684\u8fc7\u7a0b\uff0c\u5373\u201cUpcasting\u201d\u3002 \u5728\u9762\u5411\u5bf9\u8c61\u7684\u7a0b\u5e8f\u91cc\uff0c\u901a\u5e38\u90fd\u8981\u7528\u5230\u4e0a\u6eaf\u9020\u578b\u6280\u672f\u3002\u8fd9\u662f\u907f\u514d\u53bb\u8c03\u67e5\u51c6\u786e\u7c7b\u578b\u7684\u4e00\u4e2a\u597d\u529e\u6cd5 \u8bf7\u770b\u770bdoStuff()\u91cc\u7684\u4ee3\u7801\uff1a s.erase();\/\/ &#8230;s.draw(); \u00a0 \u6ce8\u610f\u5b83\u5e76\u672a\u8fd9\u6837\u8868\u8fbe\uff1a\u201c\u5982\u679c\u4f60\u662f\u4e00\u4e2aCircle\uff0c\u5c31\u8fd9\u6837\u505a\uff1b\u5982\u679c\u4f60\u662f\u4e00\u4e2aSquare\uff0c\u5c31\u90a3\u6837\u505a\uff1b\u7b49\u7b49\u201d\u3002\u82e5\u90a3\u6837\u7f16\u5199\u4ee3\u7801\uff0c\u5c31\u9700\u68c0\u67e5\u4e00\u4e2aShape\u6240\u6709\u53ef\u80fd\u7684\u7c7b\u578b\uff0c\u5982\u5706\u3001\u77e9\u5f62\u7b49\u7b49\u3002\u8fd9\u663e\u7136\u662f\u975e\u5e38\u9ebb\u70e6\u7684\uff0c\u800c\u4e14\u6bcf\u6b21\u6dfb\u52a0\u4e86\u4e00\u79cd\u65b0\u7684Shape\u7c7b\u578b\u540e\uff0c\u90fd\u8981\u76f8\u5e94\u5730\u8fdb\u884c\u4fee\u6539\u3002\u5728\u8fd9\u513f\uff0c\u6211\u4eec\u53ea\u9700\u8bf4\uff1a\u201c\u4f60\u662f\u4e00\u79cd\u51e0\u4f55\u5f62\u72b6\uff0c\u6211\u77e5\u9053\u4f60\u80fd\u5c06\u81ea\u5df1\u5220\u6389\uff0c\u5373erase()\uff1b\u8bf7\u81ea\u5df1\u91c7\u53d6\u90a3\u4e2a\u884c\u52a8\uff0c\u5e76\u81ea\u5df1\u53bb\u63a7\u5236\u6240\u6709\u7684\u7ec6\u8282\u5427\u3002\u201d<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[49],"tags":[],"_links":{"self":[{"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=\/wp\/v2\/posts\/450"}],"collection":[{"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=450"}],"version-history":[{"count":0,"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=\/wp\/v2\/posts\/450\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=450"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=450"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.huangyidong.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=450"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}