{"id":11621,"date":"2023-08-08T08:59:23","date_gmt":"2023-08-08T00:59:23","guid":{"rendered":"http:\/\/92it.top\/?p=11621"},"modified":"2023-08-08T08:59:23","modified_gmt":"2023-08-08T00:59:23","slug":"java%e4%b8%ad%e7%9a%84object%e3%80%81t%ef%bc%88%e6%b3%9b%e5%9e%8b%ef%bc%89%e3%80%81%e5%8c%ba%e5%88%ab","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=11621","title":{"rendered":"Java\u4e2d\u7684Object\u3001T\uff08\u6cdb\u578b\uff09\u3001?\u533a\u522b"},"content":{"rendered":"\n<p>\u6211\u4eec\u5148\u6765\u8bd5\u7740\u7406\u89e3\u4e00\u4e0bObject\u7c7b\uff0c\u5b66\u4e60Java\u7684\u5e94\u8be5\u90fd\u77e5\u9053Object\u662f\u6240\u6709\u7c7b\u7684\u7236\u7c7b\uff0c\u6ce8\u610f\uff1a<strong>\u90a3\u4e48\u8fd9\u5c31\u610f\u5473\u7740\u5b83\u7684\u8303\u56f4\u975e\u5e38\u5e7f\uff01<\/strong>\u9996\u5148\u8bb0\u4f4f\u8fd9\u70b9\uff0c\u5982\u679c\u4f60\u7684\u53c2\u6570\u7c7b\u578b\u65f6Object\uff0c\u90a3\u4e48\u7684\u53c2\u6570\u7c7b\u578b\u5c06\u975e\u5e38\u5e7f\uff01<\/p>\n\n\n\n<p>\u300aThinking in Java\u300b\u4e2d\u8bf4\u5f88\u591a\u539f\u56e0\u4fc3\u6210\u4e86\u6cdb\u578b\u7684\u51fa\u73b0\uff0c\u6700\u5f15\u4eba\u6ce8\u76ee\u7684\u4e00\u4e2a\u539f\u56e0\u5c31\u662f\u4e3a\u4e86\u521b\u9020\u5bb9\u5668\u7c7b\u3002\u8fd9\u4e2a\u8981\u600e\u4e48\u6765\u7406\u89e3\u5462\uff1f\u6211\u7684\u7406\u89e3\u662f\uff0c\u53ef\u4ee5\u629b\u5f00\u8fd9\u4e2a\u4e3a\u4e86\u521b\u9020\u5bb9\u5668\u7c7b\u8fd9\u4e2a\uff0c\u800c\u662f\u56de\u5230\u6cdb\u578b\u7684\u76ee\u7684\u662f<strong>\u9650\u5b9a\u67d0\u79cd\u7c7b\u578b<\/strong>\u4e0a\u6765\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u6211\u4eec\u73b0\u5728\u80fd\u5c0f\u7ed3\u4e00\u4e0bObject\u548cT\u5f88\u91cd\u8981\u7684\u4e24\u70b9\u533a\u522b\u5c31\u662f\uff1a<\/p>\n\n\n\n<ul><li>Object\u8303\u56f4\u975e\u5e38\u5e7f\uff0c\u800cT\u4ece\u4e00\u5f00\u59cb\u5c31\u4f1a\u9650\u5b9a\u8fd9\u4e2a\u7c7b\u578b\uff08\u5305\u62ec\u5b83\u53ef\u4ee5\u9650\u5b9a\u7c7b\u578b\u4e3aObject\uff09\u3002<\/li><li>Object\u7531\u4e8e\u5b83\u662f\u6240\u6709\u7c7b\u7684\u7236\u7c7b\uff0c\u6240\u4ee5\u4f1a\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\uff0c\u800cT\u4ece\u4e00\u5f00\u59cb\u5728\u7f16\u7801\u65f6\uff08\u6ce8\u610f\u662f\u5728\u5199\u4ee3\u7801\u65f6\uff09\u5c31\u9650\u5b9a\u4e86\u67d0\u79cd\u5177\u4f53\u7c7b\u578b\uff0c\u6240\u4ee5\u5b83\u4e0d\u7528\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u3002\uff08\u4e4b\u6240\u4ee5\u8981\u5f3a\u8c03\u5728\u5199\u4ee3\u7801\u65f6\u662f\u56e0\u4e3a\u6cdb\u578b\u5728\u865a\u62df\u673a\u4e2d\u4f1a\u88abJVM\u64e6\u9664\u6389\u5b83\u7684\u5177\u4f53\u7c7b\u578b\u4fe1\u606f\uff0c\u8fd9\u70b9\u53ef\u53c2\u8003\u6cdb\u578b\uff0c\u5728\u8fd9\u91cc\u4e0d\u505a\u5f15\u7533\uff09\u3002<\/li><\/ul>\n\n\n\n<p>\u6bd4\u5982\u5728jdk\u4e2d\u7684List\u7c7b\u662f\u4e2a\u6cdb\u578b\u7c7b\u3002\u73b0\u5728\u6211\u4eec\u5236\u5b9a\u5b83\u7684\u7c7b\u578b\u662fObject\u3002<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">  List&lt;Object> list = new ArrayList&lt;Object>();\n        int i = 0;\n        String s = \"s\";\n        list.add(i);\n        list.add(s);<\/pre>\n\n\n\n<p>List\u672c\u8eab\u662f\u4e2a\u6cdb\u578b\u7c7b\uff0c\u73b0\u5728\u6211\u4eec\u6307\u5b9a\u5b83\u63a5\u6536Object\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u6b64\u65f6\u5c31\u53ef\u4ee5\u653e\u7f6e\u4efb\u610f\u7c7b\u578b\u7684\u53c2\u6570\u8fdb\u53bb\uff0c\u800c\u5728\u53d6\u51fa\u6765\u662f\u5c31\u5fc5\u987b\u5f97\u8fdb\u884c\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u6210\u5177\u4f53\u7684\u7c7b\u578b\u3002<\/p>\n\n\n\n<p>\u73b0\u5728\u6211\u4eec\u5982\u679c\u5c06List\u6307\u5b9a\u63a5\u6536String\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u90a3\u4e48\u8fd9\u4e2aList\u5c31\u53ea\u80fd\u653e\u7f6eString\u7c7b\u578b\uff0c\u4e14\u53d6\u51fa\u6765\u65f6\u5c31\u4e0d\u7528\u8fdb\u884c\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u3002<\/p>\n\n\n\n<p>\u8fd9\u70b9\u7ed9\u6211\u4eec\u5e26\u6765\u7684\u542f\u793a\u662f\uff0c\u5728\u7f16\u5199\u7c7b\u4f3cList\u7c7b\u7684\u65f6\u5019\uff0c\u4e00\u5b9a\u8981\u6ce8\u610f\u662f\u5426\u7528\u6cdb\u578b\u3002\u4e00\u5b9a\u8981\u591a\u5199\u51e0\u4e2a\u6cdb\u578b\u7c7b\uff0c\u591a\u8ba8\u8bba\u591a\u7406\u89e3\uff0c\u4e0d\u7136\u8fd8\u662f\u53ef\u80fd\u4f1a\u6405\u5728\u4e00\u8d77\u3002<\/p>\n\n\n\n<p>\u63a5\u7740\u662f?\uff0c\u8fd9\u4e2a\u53ef\u80fd\u5728\u7528\u5230\u53cd\u5c04\u9700\u8981\u83b7\u53d6Class\u7c7b\u578b\u65f6\u7528\u5230\uff0c\u5b83\u7684\u89e3\u91ca\u5c31\u662f\uff1a\u63a5\u6536\u4e00\u4e2a\u4e0d\u786e\u5b9a\u7684\u7c7b\u578b\uff0c\u6709\u70b9\u548cObject\u4e00\u6837\u3002\u6211\u5bf9\u5b83\u4e00\u4e2a\u7406\u89e3\u662f\uff0c\u5982\u679c\u53ea\u7528&#8221;?&#8221;\u90a3\u4e48\u5b83\u548cObject\u662f\u4e00\u6837\u7684\uff0c\u4f46\u662f&#8221;?&#8221;\u6709\u6bd4Object\u7a0d\u5fae\u201c\u9ad8\u7ea7\u201d\u6709\u70b9\u7684\u7528\u6cd5\uff0c\u5c31\u662f\u5b83\u80fd\u7f29\u5c0f\u4e00\u4e2a\u4e0d\u786e\u5b9a\u7684\u8303\u56f4\uff0c\u5229\u7528\u7c7b\u4f3c&#8221;? extends Test&#8221;\uff0c\u8fd9\u5c31\u610f\u5473\u7740\u53ea\u63a5\u6536\u63a5\u6536Test\u7c7b\u7684\u7ee7\u627f\u7c7b\uff0c\u662f\u4e0d\u662f\u6bd4Object\u7684\u8303\u56f4\u7f29\u5c0f\u4e86\uff1f<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">        \/\/\u5bf9\u4e8e\u7c7b Object\uff0cT\u53ef\u4ee5\u4fee\u9970\u7c7b\uff0c?\u4e0d\u80fd\u4fee\u9970\u7c7b\n     \n        class A1 {\n        }\n     \n        class A2&lt;T> {\n        }\n     \n        class A3&lt;?> { \/\/\u7f16\u8bd1\u5668\u63d0\u793a\u4ee3\u7801\u9519\u8bef\n        }\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/\u5bf9\u4e8e\u65b9\u6cd5\u53c2\u6570  T\u548cObject\u7c7b\u578b\u7684\u53c2\u6570\u53ef\u8c03\u7528\u7684\u65b9\u6cd5\u662f\u4e00\u6837\u7684,&lt;?>\u5fc5\u987b\u57fa\u4e8e&lt;T>\u6216&lt;Object>\u6765\u4f7f\u7528\uff0c\u5c31\u662f\u4e00\u4e2a\u901a\u914d\u7b26\uff0c\u6307\u4ee3\u6240\u6709\u7c7b\u578b\n    public &lt;T> T getT(T t) {\n        t.getClass();\n        return (T)t;\n    }\n \n    public Object getO(Object o) {\n        o.getClass();\n        return (Object)o;\n    }\n \n    public List&lt;?> get(List&lt;?> o) {\n        int a = o.size();\n        return (List&lt;?>) o;\n    }\n \n    public void test() {\n        BB&lt;?> bb = new BB&lt;>();\n    }\n \n    class BB&lt;Object>{}\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/\u5bf9\u4e8e\u65b9\u6cd5\u8fd4\u56de\u503c&lt;T>\u548c&lt;?>\u53ef\u4ee5\u66f4\u7cbe\u786e\u7684\u9650\u5236\u7c7b\u578b\n    public &lt;T extends String> T getT2(T t) {\n        t.getClass();\n        return t;\n    }\n \n    public Object getO2(Object o) {\n        return o;\n    }\n \n    public List&lt;? extends String> get2(List&lt;?> l) {\n        int a = l.size();\n        return (List&lt;String>) l;\n    }\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"> \/\/\u65b9\u6cd5\u8fd4\u56de\u503c\u4e0d\u80fd\u7528&lt;T>,\u53ef\u4ee5\u7528&lt;?>\n&lt;T>\u4e0d\u662f\u4e00\u4e2a\u5b9e\u9645\u7c7b\uff0c\u5b83\u8d77\u4e00\u4e2a\u6307\u4ee3\u4f5c\u7528\uff0c\u4ee3\u66ff\u67d0\u4e2a\u7c7b\uff0c\u5c31\u662f\u5360\u4f4d\u7b26\uff0c\u8bf4\u660e\u8fd9\u91cc\u9700\u8981\u6307\u5b9a\u4e00\u4e2a\u7c7b\u578b\u3002\nObject\u662f\u5b9e\u9645\u7684\u7c7b\uff0c\n&lt;?>\u662f\u4e00\u4e2a\u901a\u914d\u7b26\u53f7\uff0c\u5982\u4e0b\u8868\u793a\u8fd9\u4e2a\u7c7b\u4e0d\u6307\u5b9a\u7c7b\u578b\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528extends\u548csuper\u9650\u5236\u5339\u914d\n \n    public A2&lt;T> getT3() { \/\/\u7f16\u8bd1\u5668\u63d0\u793a\u4ee3\u7801\u9519\u8bef\n        return null;\n    }\n    \n    public A2&lt;Object> getO3() {\n        return null;\n    }\n \n    public A2&lt;?> get3() {\n        return null;\n    }\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\n     \/\/\u65b9\u6cd5\u8fd4\u56de\u503c\u4e2d&lt;T>\u548c&lt;?>\u90fd\u53ef\u4ee5\u7528\u6307\u5b9a\u7236\u7c7b\u7684\u65b9\u5f0f\u9650\u5b9a\u8fd4\u56de\u503c\u7c7b\u578b\n        public &lt;T extends String> T getT4() {\n            return null;\n        }\n     \n        public A2&lt;? extends String> get4() {\n            return null;\n        }\n     \n        \/\/\u4ee5\u4e0a\u4e24\u4e2a\u65b9\u6cd5\u6548\u679c\u7b49\u540c\u8fd9\u4e2a\u65b9\u6cd5\uff0c\u4e5f\u5c31\u662f\u58f0\u660e\u7236\u7c7b\u4f5c\u4e3a\u8fd4\u56de\u503c\uff08\u8fd9\u91cc\u5047\u8bbe\u6709\u7c7b\u7ee7\u627f\u4e86String\uff09\n        public String getO4() {\n            return null;\n        }\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/\u65b9\u6cd5\u8fd4\u56de\u503c\u53ef\u4ee5\u7528&lt;?>\u6307\u5b9a\u5b50\u7c7b\u7c7b\u578b\uff0c\u4e0d\u80fd\u7528&lt;T>;\u4e2a\u4eba\u89c9\u5f97\u610f\u4e49\u4e0d\u5927\uff0c\u7528super\u7684\u5730\u65b9\u5e94\u8be5\u7528extends\u4e5f\u4e00\u6837\n    public &lt;T super String> T getT5() { \/\/\u7f16\u8bd1\u5668\u63d0\u793a\u4ee3\u7801\u9519\u8bef\n        return null;\n    }\n \n    public A2&lt;? super String> get5() {\n        return null;\n    }\n<\/pre>\n\n\n\n<p><strong>\u603b\u7ed3\uff1a<\/strong><\/p>\n\n\n\n<p>1\u3001Object\u662f\u6240\u6709\u7c7b\u7684\u7236\u7c7b\uff0c\u4ee3\u8868\u6240\u6709\u7c7b\uff1b\u662f\u5360\u4f4d\u7b26\uff0c\u8868\u793a\u9700\u8981\u4e00\u4e2a\u7c7b\u578b\uff1b\u901a\u914d\u7b26\uff0c\u5339\u914d\u6240\u6709\u7c7b\u578b\u3002<\/p>\n\n\n\n<p>2\u3001\u76f8\u5bf9\u4e8eObject\uff0c\u6cdb\u578b\u901a\u8fc7\u6307\u5b9a\u7236\u7c7b\u53ef\u4ee5\u7f29\u5c0f\u9650\u5236\u8303\u56f4\uff0c\u53ef\u4ee5\u9650\u5b9a\u5339\u914d\u7684\u7c7b\u578b\u7684\u7236\u7c7b\u6216\u5b50\u7c7b\u3002<\/p>\n\n\n\n<p>3\u3001\u6cdb\u578b\u53ef\u4ee5\u57fa\u4e8e\u7528\u6237\u6307\u5b9a\u7684\u7c7b\u578b\u8fdb\u884c\u663e\u5f0f\u6216\u9690\u5f0f\u7684\u7c7b\u578b\u8f6c\u6362\uff0c\u5728\u7f16\u8bd1\u65f6\u8fdb\u884c\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5\uff0c\u76f8\u5bf9\u4e8eObject\u907f\u514d\u4e86\u7c7b\u578b\u8f6c\u6362\u5f02\u5e38\u3002<\/p>\n\n\n\n<p>4\u3001\u7684\u597d\u5904\u662f\u5b9a\u4e49\u4e00\u4e2a\u5f15\u7528\u53d8\u91cf\uff0c\u53ef\u4ee5\u6307\u5411\u591a\u4e2a\u5bf9\u8c61\u3002<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">        List&lt;?> list = new ArrayList&lt;>();\n        list = new ArrayList&lt;String>();\n        list = new ArrayList&lt;Integer>();\n \n        List&lt;Object> list2 = new ArrayList&lt;>();\n        list2 = new ArrayList&lt;Object>(); \u221a\n        list2 = new ArrayList&lt;Integer>(); \u00d7<\/pre>\n\n\n\n<p><br><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6211\u4eec\u5148\u6765\u8bd5\u7740\u7406\u89e3\u4e00\u4e0bObject\u7c7b\uff0c\u5b66\u4e60Java\u7684\u5e94\u8be5\u90fd\u77e5\u9053Object\u662f\u6240\u6709\u7c7b\u7684\u7236\u7c7b\uff0c\u6ce8\u610f\uff1a\u90a3\u4e48\u8fd9\u5c31\u610f\u5473\u7740\u5b83 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