{"id":1265,"date":"2022-10-28T23:02:16","date_gmt":"2022-10-28T15:02:16","guid":{"rendered":"https:\/\/qaqaq.top\/?p=1265"},"modified":"2022-11-27T12:39:47","modified_gmt":"2022-11-27T04:39:47","slug":"%e6%b3%9b%e5%9e%8b%e4%b8%8efile-%e6%b3%9b%e5%9e%8b%e5%9c%a8%e7%bb%a7%e6%89%bf%e6%96%b9%e9%9d%a2%e7%9a%84%e4%bd%93%e7%8e%b0%e3%80%81%e9%80%9a%e9%85%8d%e7%ac%a6%e7%9a%84%e4%bd%bf%e7%94%a8%e3%80%81","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=1265","title":{"rendered":"\u6cdb\u578b\u4e0eFile-\u6cdb\u578b\u5728\u7ee7\u627f\u65b9\u9762\u7684\u4f53\u73b0\u3001\u901a\u914d\u7b26\u7684\u4f7f\u7528\u3001\u4f7f\u7528\u901a\u914d\u7b26\u540e\u6570\u636e\u7684\u8bfb\u53d6\u548c\u5199\u5165\u8981\u6c42\u3001\u6709\u9650\u5236\u6761\u4ef6\u7684\u901a\u914d\u7b26\u7684\u4f7f\u7528"},"content":{"rendered":"\n
package top.qaqaq.java.P572;\r\n\r\nimport org.junit.jupiter.api.Test;\r\n\r\nimport java.util.AbstractList;\r\nimport java.util.ArrayList;\r\nimport java.util.Iterator;\r\nimport java.util.List;\r\n\r\n\/**\r\n * 1. \u6cdb\u578b\u5728\u7ee7\u627f\u65b9\u9762\u7684\u4f53\u73b0\r\n *\r\n * 2. \u901a\u914d\u7b26\u7684\u4f7f\u7528\r\n *\r\n * @author RichieZhang\r\n * @create 2022-10-28 \u4e0b\u5348 9:33\r\n *\/\r\npublic class GenericTest {\r\n\r\n    \/*\r\n    1. \u6cdb\u578b\u5728\u7ee7\u627f\u65b9\u9762\u7684\u4f53\u73b0\r\n\r\n    \u867d\u7136\u7c7bA\u662f\u7c7bB\u7684\u7236\u7c7b\uff0c\u4f46\u662fG<A> \u548c G<B>\u4e8c\u8005\u4e0d\u5177\u5907\u5b50\u7236\u7c7b\u5173\u7cfb\uff0c\u4e8c\u8005\u662f\u5e76\u5217\u5173\u7cfb\u3002\r\n\r\n        \u8865\u5145\uff1a\u7c7bA\u662f\u7c7bB\u7684\u7236\u7c7b\uff0cA<G> \u662f B<G> \u7684\u7236\u7c7b\r\n\r\n     *\/\r\n    @Test\r\n    public void test1(){\r\n\r\n        Object obj = null;\r\n        String str = null;\r\n        obj = str;\r\n\r\n        Object[] arr1 = null;\r\n        String[] arr2 = null;\r\n        arr1 = arr2;\r\n\r\n        \/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7\r\n\/\/        Date date = new Date();\r\n\/\/        str = date;\r\n        List<Object> list1 = null;\r\n        List<String> list2 = new ArrayList<String>();\r\n        \/\/\u6b64\u65f6\u7684list1\u548clist2\u7684\u7c7b\u578b\u4e0d\u5177\u6709\u5b50\u7236\u7c7b\u5173\u7cfb\r\n        \/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7\r\n\/\/        list1 = list2;\r\n\r\n        \/*\r\n        \u53cd\u8bc1\u6cd5\uff1a\r\n        \u5047\u8bbelist1 = list2;\r\n        list1.add(123);\u5bfc\u81f4\u6df7\u5165\u975eString\u7684\u6570\u636e\u3002\u51fa\u9519\u3002\r\n\r\n\r\n         *\/\r\n\r\n        show(list1);\r\n        show1(list2);\r\n    }\r\n\r\n    public void show1(List<String> list){\r\n\r\n    }\r\n\r\n    public void show(List<Object> list){\r\n\r\n    }\r\n\r\n    @Test\r\n    public void test2(){\r\n\r\n        AbstractList<String> list1 = null;\r\n        List<String> list2 = null;\r\n        ArrayList<String> list3 = null;\r\n        list1 = list3;\r\n        list2 = list3;\r\n\r\n        List<String> list = new ArrayList<>();\r\n    }\r\n\r\n    \/*\r\n    2. \u901a\u914d\u7b26\u7684\u4f7f\u7528\r\n        \u901a\u914d\u7b26\uff1a\uff1f\r\n\r\n        \u7c7bA\u662f\u7c7bB\u7684\u7236\u7c7b\uff0cG<A>\u548cG<B>\u662f\u6ca1\u6709\u5173\u7cfb\u7684\uff0c\u4e8c\u8005\u516c\u540c\u7684\u7236\u7c7b\u662f\uff1aG<?>\r\n     *\/\r\n\r\n    @Test\r\n    public void test3(){\r\n        List<Object> list1 = null;\r\n        List<String> list2 = null;\r\n\r\n        List<?> list = null;\r\n\r\n        list = list1;\r\n        list = list2;\r\n        \/\/\u7f16\u8bd1\u901a\u8fc7\r\n\/\/        print(list1);\r\n\/\/        print(list2);\r\n\r\n        \/\/\r\n        List<String> list3 = new ArrayList<>();\r\n        list3.add(\"AA\");\r\n        list3.add(\"BB\");\r\n        list3.add(\"CC\");\r\n        list = list3;\r\n        \/\/\u6dfb\u52a0(\u5199\u5165)\uff1a\u5bf9\u4e8eList<?>\u5c31\u4e0d\u80fd\u5411\u5176\u5185\u90e8\u6dfb\u52a0\u6570\u636e\u3002\r\n        \/\/\u9664\u4e86\u6dfb\u52a0null\u4e4b\u5916\u3002\r\n\/\/        list.add(\"DD\");\r\n\/\/        list.add('?');\r\n\r\n        list.add(null);\r\n\r\n        \/\/\u83b7\u53d6(\u8bfb\u53d6)\uff1a\u5141\u8bb8\u8bfb\u53d6\u6570\u636e\uff0c\u8bfb\u53d6\u7684\u6570\u636e\u7c7b\u578b\u4e3aObject\u3002\r\n        Object o = list.get(0);\r\n        System.out.println(o);\r\n\r\n    }\r\n\r\n    public void print(List<?> list){\r\n        Iterator<?> iterator = list.iterator();\r\n        while (iterator.hasNext()){\r\n            Object obj = iterator.next();\r\n            System.out.println(obj);\r\n        }\r\n    }\r\n\r\n    \/*\r\n    3. \u6709\u9650\u5236\u6761\u4ef6\u7684\u901a\u914d\u7b26\u7684\u4f7f\u7528\u3002\r\n        ? extends A:\r\n                G<? extends A> \u53ef\u4ee5\u4f5c\u4e3aG<A>\u548cG<B>\u7684\u7236\u7c7b\uff0c\u5176\u4e2dB\u662fA\u7684\u5b50\u7c7b\r\n\r\n        ? super A:\r\n                G<? super A> \u53ef\u4ee5\u4f5c\u4e3aG<A>\u548cG<B>\u7684\u7236\u7c7b\uff0c\u5176\u4e2dB\u662fA\u7684\u7236\u7c7b\r\n     *\/\r\n\r\n    @Test\r\n    public void test4(){\r\n        List<? extends Person> list1 = null;\r\n        List<? super Person> list2 = null;\r\n\r\n        List<Student> list3 = new ArrayList<Student>();\r\n        List<Person> list4 = new ArrayList<Person>();\r\n        List<Object> list5 = new ArrayList<Object>();\r\n\r\n        list1 = list3;\r\n        list1 = list4;\r\n\/\/        list1 = list5;\r\n\r\n\/\/        list2 = list3;\r\n        list2 = list4;\r\n        list2 = list5;\r\n\r\n        \/\/\u8bfb\u53d6\u6570\u636e\uff1a\r\n        list1 = list3;\r\n        Person p = list1.get(0);\r\n        \/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7\r\n\/\/        Student s = list1.get(0);\r\n\r\n        list2 = list4;\r\n        Object obj = list2.get(0);\r\n        \/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7\r\n\/\/        Person obj = list2.get(0);\r\n\r\n        \/\/\u5199\u5165\u6570\u636e\uff1a\r\n        \/\/\u7f16\u8bd1\u4e0d\u901a\u8fc7\r\n\/\/        list1.add(new Student());\r\n\r\n        \/\/\u7f16\u8bd1\u901a\u8fc7\r\n        list2.add(new Person());\r\n        list2.add(new Student());\r\n    }\r\n}\r\n<\/code><\/pre>\n\n\n\n
package top.qaqaq.java.P572;\r\n\r\n\/**\r\n * @author RichieZhang\r\n * @create 2022-10-28 \u4e0b\u5348 10:15\r\n *\/\r\npublic class Person {\r\n}\r\n<\/code><\/pre>\n\n\n\n
package top.qaqaq.java.P572;\r\n\r\n\/**\r\n * @author RichieZhang\r\n * @create 2022-10-28 \u4e0b\u5348 10:15\r\n *\/\r\npublic class Student extends Person{\r\n}\r\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[46],"class_list":["post-1265","post","type-post","status-publish","format-standard","hentry","category-java-code","tag-java"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1265"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1265"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1265\/revisions"}],"predecessor-version":[{"id":1266,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1265\/revisions\/1266"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1265"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1265"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1265"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}