{"id":2498,"date":"2026-09-24T09:00:00","date_gmt":"2026-09-24T09:00:00","guid":{"rendered":"https:\/\/otus.ru\/journal\/?p=2498"},"modified":"2026-09-25T15:30:37","modified_gmt":"2026-09-25T15:30:37","slug":"poleznosti-java-chto-dolzhen-znat-programmist-o-dzhenerikah","status":"publish","type":"post","link":"https:\/\/otus.ru\/journal\/poleznosti-java-chto-dolzhen-znat-programmist-o-dzhenerikah\/","title":{"rendered":"\u0414\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438 \u0432 Java: \u0447\u0442\u043e \u044d\u0442\u043e \u0442\u0430\u043a\u043e\u0435 \u0438 \u0434\u043b\u044f \u0447\u0435\u0433\u043e \u043e\u043d\u0438 \u043d\u0443\u0436\u043d\u044b"},"content":{"rendered":"

\u0414\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438 (generics)<\/strong> \u0432 Java — \u044d\u0442\u043e \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u0438\u0437\u0430\u0446\u0438\u0438 \u0442\u0438\u043f\u043e\u0432: \u043a\u043b\u0430\u0441\u0441, \u0438\u043d\u0442\u0435\u0440\u0444\u0435\u0439\u0441 \u0438\u043b\u0438 \u043c\u0435\u0442\u043e\u0434 \u043e\u0431\u044a\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u0441 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u043e\u043c \u0442\u0438\u043f\u0430 (<T><\/code>), \u0430 \u043a\u043e\u043d\u043a\u0440\u0435\u0442\u043d\u044b\u0439 \u0442\u0438\u043f (String<\/code>, Integer<\/code>) \u043f\u043e\u0434\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u043f\u0440\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0438. \u041d\u0443\u0436\u043d\u044b \u043e\u043d\u0438 \u0434\u043b\u044f \u0442\u043e\u0433\u043e, \u0447\u0442\u043e\u0431\u044b \u043e\u0448\u0438\u0431\u043a\u0443 \u00ab\u043f\u043e\u043b\u043e\u0436\u0438\u043b\u0438 \u0432 \u043a\u043e\u043b\u043b\u0435\u043a\u0446\u0438\u044e \u043d\u0435 \u0442\u043e\u0442 \u0442\u0438\u043f\u00bb \u043b\u043e\u0432\u0438\u043b \u043a\u043e\u043c\u043f\u0438\u043b\u044f\u0442\u043e\u0440, \u0430 \u043d\u0435 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044c \u0432\u043e \u0432\u0440\u0435\u043c\u044f \u0440\u0430\u0431\u043e\u0442\u044b \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u044b, \u0438 \u0447\u0442\u043e\u0431\u044b \u043a\u043e\u0434 \u043d\u0435 \u0431\u044b\u043b \u0437\u0430\u0441\u0442\u0430\u0432\u043b\u0435\u043d \u0440\u0443\u0447\u043d\u044b\u043c\u0438 \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u044f\u043c\u0438 (String) obj<\/code>.<\/p>\n

\n

\u0421\u043e\u0434\u0435\u0440\u0436\u0430\u043d\u0438\u0435<\/strong><\/p>\n

    \n
  1. \u041c\u0438\u043d\u0438-\u0441\u043b\u043e\u0432\u0430\u0440\u044c: \u043f\u044f\u0442\u044c \u0442\u0435\u0440\u043c\u0438\u043d\u043e\u0432, \u043a\u043e\u0442\u043e\u0440\u044b\u0435 \u043f\u0443\u0442\u0430\u044e\u0442<\/a><\/li>\n
  2. \u0417\u0430\u0447\u0435\u043c \u043d\u0443\u0436\u043d\u044b \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438: \u043e\u0448\u0438\u0431\u043a\u0430 \u0434\u043e \u0438 \u043f\u043e\u0441\u043b\u0435<\/a><\/li>\n
  3. \u041c\u0438\u043d\u0438\u043c\u0430\u043b\u044c\u043d\u044b\u0439 \u0440\u0430\u0431\u043e\u0447\u0438\u0439 \u043f\u0440\u0438\u043c\u0435\u0440: \u043a\u043b\u0430\u0441\u0441, \u043c\u0435\u0442\u043e\u0434 \u0438 \u043e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u0435<\/a><\/li>\n
  4. \u0418\u043d\u0432\u0430\u0440\u0438\u0430\u043d\u0442\u043d\u043e\u0441\u0442\u044c: \u043f\u043e\u0447\u0435\u043c\u0443 List<Integer><\/code> — \u043d\u0435 List<Number><\/code><\/a><\/li>\n
  5. Wildcard: ? extends<\/code>, ? super<\/code> \u0438 \u043f\u0440\u0430\u0432\u0438\u043b\u043e PECS<\/a><\/li>\n
  6. \u0421\u0442\u0438\u0440\u0430\u043d\u0438\u0435 \u0442\u0438\u043f\u043e\u0432 \u0438 \u0435\u0433\u043e \u043f\u043e\u0441\u043b\u0435\u0434\u0441\u0442\u0432\u0438\u044f<\/a><\/li>\n
  7. Raw types \u0438 \u0437\u0430\u0433\u0440\u044f\u0437\u043d\u0435\u043d\u0438\u0435 \u043a\u0443\u0447\u0438<\/a><\/li>\n
  8. \u0421\u043e\u0433\u043b\u0430\u0448\u0435\u043d\u0438\u0435 \u043e\u0431 \u0438\u043c\u0435\u043d\u0430\u0445 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u043e\u0432<\/a><\/li>\n
  9. \u0415\u0441\u043b\u0438 \u043d\u0435 \u043a\u043e\u043c\u043f\u0438\u043b\u0438\u0440\u0443\u0435\u0442\u0441\u044f: \u0441\u0438\u043c\u043f\u0442\u043e\u043c -> \u043f\u0440\u0438\u0447\u0438\u043d\u0430<\/a><\/li>\n
  10. \u0412\u044b\u0432\u043e\u0434\u044b<\/a><\/li>\n
  11. \u0413\u0434\u0435 \u043f\u0440\u0438\u043c\u0435\u043d\u044f\u0435\u0442\u0441\u044f \/ \u0441\u0432\u044f\u0437\u044c \u0441 \u043f\u0440\u0430\u043a\u0442\u0438\u043a\u043e\u0439<\/a><\/li>\n
  12. FAQ<\/a><\/li>\n<\/ol>\n<\/div>\n

    \u0412\u0430\u0436\u043d\u0430\u044f \u0433\u0440\u0430\u043d\u0438\u0446\u0430: \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438 \u0440\u0430\u0431\u043e\u0442\u0430\u044e\u0442 \u043d\u0430 \u044d\u0442\u0430\u043f\u0435 \u043a\u043e\u043c\u043f\u0438\u043b\u044f\u0446\u0438\u0438. \u0412 \u0431\u0430\u0439\u0442-\u043a\u043e\u0434\u0435 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u044b \u0442\u0438\u043f\u043e\u0432 \u0432 \u043e\u0441\u043d\u043e\u0432\u043d\u043e\u043c \u0441\u0442\u0438\u0440\u0430\u044e\u0442\u0441\u044f (type erasure), \u043f\u043e\u044d\u0442\u043e\u043c\u0443 List<String><\/code> \u0438 List<Integer><\/code> \u0432\u043e \u0432\u0440\u0435\u043c\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f — \u043e\u0434\u0438\u043d \u0438 \u0442\u043e\u0442 \u0436\u0435 \u043a\u043b\u0430\u0441\u0441 ArrayList<\/code>. \u0418\u0437 \u044d\u0442\u043e\u0433\u043e \u0441\u043b\u0435\u0434\u0443\u044e\u0442 \u043f\u043e\u0447\u0442\u0438 \u0432\u0441\u0435 \u043e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u044f \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u043e\u0432, \u043e \u043a\u043e\u0442\u043e\u0440\u044b\u0445 \u043d\u0438\u0436\u0435. \u041f\u0440\u0438\u043c\u0435\u0440\u044b \u043f\u0440\u043e\u0432\u0435\u0440\u0435\u043d\u044b \u043d\u0430 OpenJDK 25.0.4 (Java 25 LTS) 24.09.2026.<\/p>\n

    \u041c\u0438\u043d\u0438-\u0441\u043b\u043e\u0432\u0430\u0440\u044c: \u043f\u044f\u0442\u044c \u0442\u0435\u0440\u043c\u0438\u043d\u043e\u0432, \u043a\u043e\u0442\u043e\u0440\u044b\u0435 \u043f\u0443\u0442\u0430\u044e\u0442<\/h2>\n\n\n\n\n\n\n\n\n\n
    \u0422\u0435\u0440\u043c\u0438\u043d<\/th>\n\u041f\u0440\u0438\u043c\u0435\u0440<\/th>\n\u0427\u0442\u043e \u044d\u0442\u043e<\/th>\n<\/tr>\n<\/thead>\n
    \u041f\u0430\u0440\u0430\u043c\u0435\u0442\u0440 \u0442\u0438\u043f\u0430<\/td>\nT<\/code> \u0432 class Box<T><\/code><\/td>\n\u00ab\u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u0430\u044f\u00bb \u0434\u043b\u044f \u0442\u0438\u043f\u0430 \u0432 \u043e\u0431\u044a\u044f\u0432\u043b\u0435\u043d\u0438\u0438<\/td>\n<\/tr>\n
    \u0410\u0440\u0433\u0443\u043c\u0435\u043d\u0442 \u0442\u0438\u043f\u0430<\/td>\nString<\/code> \u0432 Box<String><\/code><\/td>\n\u043a\u043e\u043d\u043a\u0440\u0435\u0442\u043d\u044b\u0439 \u0442\u0438\u043f \u043f\u0440\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0438<\/td>\n<\/tr>\n
    \u041f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u0438\u0437\u043e\u0432\u0430\u043d\u043d\u044b\u0439 \u0442\u0438\u043f<\/td>\nList<String><\/code><\/td>\n\u0442\u0438\u043f \u0441 \u043f\u043e\u0434\u0441\u0442\u0430\u0432\u043b\u0435\u043d\u043d\u044b\u043c \u0430\u0440\u0433\u0443\u043c\u0435\u043d\u0442\u043e\u043c<\/td>\n<\/tr>\n
    Raw type (\u0441\u044b\u0440\u043e\u0439 \u0442\u0438\u043f)<\/td>\nList<\/code> \u0431\u0435\u0437 <...><\/code><\/td>\n\u043e\u0431\u043e\u0431\u0449\u0435\u043d\u043d\u044b\u0439 \u0442\u0438\u043f \u0431\u0435\u0437 \u0430\u0440\u0433\u0443\u043c\u0435\u043d\u0442\u0430, \u043d\u0430\u0441\u043b\u0435\u0434\u0438\u0435 \u0434\u043e Java 5<\/td>\n<\/tr>\n
    Wildcard<\/td>\nList<? extends Number><\/code><\/td>\n\u00ab\u043a\u0430\u043a\u043e\u0439-\u0442\u043e \u0442\u0438\u043f\u00bb \u0441 \u0433\u0440\u0430\u043d\u0438\u0446\u0435\u0439, \u0442\u043e\u043b\u044c\u043a\u043e \u0432 \u043c\u0435\u0441\u0442\u0430\u0445 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \u0417\u0430\u0447\u0435\u043c \u043d\u0443\u0436\u043d\u044b \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438: \u043e\u0448\u0438\u0431\u043a\u0430 \u0434\u043e \u0438 \u043f\u043e\u0441\u043b\u0435<\/h2>\n

    \u0414\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438 \u043f\u043e\u044f\u0432\u0438\u043b\u0438\u0441\u044c \u0432 Java 5 (2004). \u0414\u043e \u044d\u0442\u043e\u0433\u043e \u043a\u043e\u043b\u043b\u0435\u043a\u0446\u0438\u0438 \u0445\u0440\u0430\u043d\u0438\u043b\u0438 Object<\/code>, \u0438 \u0442\u0438\u043f \u043f\u0440\u043e\u0432\u0435\u0440\u044f\u043b\u0441\u044f \u0442\u043e\u043b\u044c\u043a\u043e \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u0435\u043c \u043f\u0440\u0438 \u0447\u0442\u0435\u043d\u0438\u0438. \u0412\u043e\u0442 \u043a\u0430\u043a \u044d\u0442\u043e \u0432\u044b\u0433\u043b\u044f\u0434\u0438\u0442 (raw type — \u0442\u0430\u043a \u043f\u0438\u0441\u0430\u043b\u0438 \u0434\u043e Java 5):<\/p>\n

    import<\/span> <\/span>java.util.ArrayList<\/span>;<\/span>\nimport<\/span> <\/span>java.util.List<\/span>;<\/span>\n\npublic<\/span> <\/span>class<\/span> Main<\/span> {<\/span>\n    <\/span>public<\/span> <\/span>static<\/span> <\/span>void<\/span> <\/span>main<\/span>(<\/span>String<\/span>[]<\/span> <\/span>args<\/span>) {<\/span>\n        <\/span>List<\/span> <\/span>names<\/span> <\/span>=<\/span> <\/span>new<\/span> <\/span>ArrayList<\/span>();      <\/span>\/\/ raw type: \u0431\u0435\u0437 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u0430<\/span>\n        <\/span>names<\/span>.<\/span>add<\/span>(<\/span>\"\u0410\u043d\u043d\u0430\"<\/span>);<\/span>\n        <\/span>names<\/span>.<\/span>add<\/span>(<\/span>42<\/span>);                     <\/span>\/\/ \u043a\u043e\u043c\u043f\u0438\u043b\u044f\u0442\u043e\u0440 \u043d\u0435 \u0432\u043e\u0437\u0440\u0430\u0436\u0430\u0435\u0442<\/span>\n        <\/span>for<\/span> (<\/span>Object<\/span> <\/span>o<\/span> : <\/span>names<\/span>) {<\/span>\n            <\/span>String<\/span> <\/span>s<\/span> <\/span>=<\/span> (<\/span>String<\/span>) <\/span>o<\/span>;         <\/span>\/\/ \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u0435 \u0432\u0440\u0443\u0447\u043d\u0443\u044e<\/span>\n            <\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>s<\/span>.<\/span>toUpperCase<\/span>());<\/span>\n        }<\/span>\n    }<\/span>\n}<\/span><\/code><\/pre>\n
    \u041a\u043e\u043c\u043f\u0438\u043b\u044f\u0446\u0438\u044f \u043f\u0440\u043e\u0445\u043e\u0434\u0438\u0442, javac \u043b\u0438\u0448\u044c \u043f\u0440\u0435\u0434\u0443\u043f\u0440\u0435\u0436\u0434\u0430\u0435\u0442 Note: Main.java uses unchecked or unsafe operations.<\/code> (\u043f\u0440\u0438 \u0437\u0430\u043f\u0443\u0441\u043a\u0435 \u0431\u0435\u0437 \u043a\u043e\u043c\u043f\u0438\u043b\u044f\u0446\u0438\u0438 java Main.java<\/code> \u0432\u043c\u0435\u0441\u0442\u043e Note \u0441\u0440\u0430\u0437\u0443 \u043f\u0435\u0447\u0430\u0442\u0430\u044e\u0442\u0441\u044f \u043f\u043e\u0434\u0440\u043e\u0431\u043d\u044b\u0435 \u043f\u0440\u0435\u0434\u0443\u043f\u0440\u0435\u0436\u0434\u0435\u043d\u0438\u044f [unchecked] unchecked call to add(E) as a member of the raw type List<\/code>). \u041f\u0440\u0438 \u0437\u0430\u043f\u0443\u0441\u043a\u0435 \u043f\u0435\u0440\u0432\u0430\u044f \u0441\u0442\u0440\u043e\u043a\u0430 \u043f\u0435\u0447\u0430\u0442\u0430\u0435\u0442\u0441\u044f, \u0430 \u043d\u0430 \u0432\u0442\u043e\u0440\u043e\u0439 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u0430 \u043f\u0430\u0434\u0430\u0435\u0442:<\/p>\n
    \u0410\u041d\u041d\u0410\nException in thread "main" java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.String (java.lang.Integer and java.lang.String are in module java.base of loader 'bootstrap')\n    at Main.main(Main.java:10)\n<\/code><\/pre>\n
    \u0418\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u0435 — \u0443\u043a\u0430\u0437\u0430\u0442\u044c \u0442\u0438\u043f \u044d\u043b\u0435\u043c\u0435\u043d\u0442\u043e\u0432: List<String> names = new ArrayList<>();<\/code>. \u0422\u0435\u043f\u0435\u0440\u044c \u0442\u0430 \u0436\u0435 \u0441\u0442\u0440\u043e\u043a\u0430 names.add(42);<\/code> \u043d\u0435 \u043a\u043e\u043c\u043f\u0438\u043b\u0438\u0440\u0443\u0435\u0442\u0441\u044f:<\/p>\n
    Main.java:8: error: incompatible types: int cannot be converted to String\n        names.add(42);\n                  ^\n<\/code><\/pre>\n
    \u041e\u0448\u0438\u0431\u043a\u0430 \u043f\u0435\u0440\u0435\u0435\u0445\u0430\u043b\u0430 \u0438\u0437 \u0440\u0430\u043d\u0442\u0430\u0439\u043c\u0430 (\u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044f) \u0432 \u043a\u043e\u043c\u043f\u0438\u043b\u044f\u0446\u0438\u044e (\u0443 \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430), \u0430 \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u0435 (String) o<\/code> \u0431\u043e\u043b\u044c\u0448\u0435 \u043d\u0435 \u043d\u0443\u0436\u043d\u043e: for (String s : names)<\/code>. \u042d\u0442\u043e \u0438 \u0435\u0441\u0442\u044c \u0433\u043b\u0430\u0432\u043d\u044b\u0439 \u043e\u0442\u0432\u0435\u0442 \u043d\u0430 \u0432\u043e\u043f\u0440\u043e\u0441, \u0434\u043b\u044f \u0447\u0435\u0433\u043e \u043d\u0443\u0436\u043d\u044b \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u0438: \u0442\u0438\u043f\u043e\u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u044c \u0431\u0435\u0437 \u0440\u0443\u0447\u043d\u044b\u0445 \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u0439 \u043f\u043b\u044e\u0441 \u043e\u0434\u0438\u043d \u043a\u043e\u0434 \u0434\u043b\u044f \u043c\u043d\u043e\u0433\u0438\u0445 \u0442\u0438\u043f\u043e\u0432.<\/p>\n
    \u041c\u0438\u043d\u0438\u043c\u0430\u043b\u044c\u043d\u044b\u0439 \u0440\u0430\u0431\u043e\u0447\u0438\u0439 \u043f\u0440\u0438\u043c\u0435\u0440: \u043a\u043b\u0430\u0441\u0441, \u043c\u0435\u0442\u043e\u0434 \u0438 \u043e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u0435<\/h2>\n
    \u041e\u0434\u0438\u043d \u0444\u0430\u0439\u043b \u043f\u043e\u043a\u0430\u0437\u044b\u0432\u0430\u0435\u0442 \u0442\u0440\u0438 \u0444\u043e\u0440\u043c\u044b \u0434\u0436\u0435\u043d\u0435\u0440\u0438\u043a\u043e\u0432 \u0441\u0440\u0430\u0437\u0443. \u0421\u043e\u0445\u0440\u0430\u043d\u0438\u0442\u0435 \u043a\u0430\u043a Main.java<\/code>, \u0437\u0430\u043f\u0443\u0441\u0442\u0438\u0442\u0435 java Main.java<\/code> (Java 11+ \u0443\u043c\u0435\u0435\u0442 \u0437\u0430\u043f\u0443\u0441\u043a\u0430\u0442\u044c \u043e\u0434\u0438\u043d \u0444\u0430\u0439\u043b \u0431\u0435\u0437 \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u043e\u0433\u043e javac<\/code>).<\/p>\n
    import<\/span> <\/span>java.util.ArrayList<\/span>;<\/span>\nimport<\/span> <\/span>java.util.List<\/span>;<\/span>\nimport<\/span> <\/span>java.util.function.Function<\/span>;<\/span>\n\npublic<\/span> <\/span>class<\/span> Main<\/span> {<\/span>\n\n    <\/span>\/\/ \u041e\u0431\u043e\u0431\u0449\u0435\u043d\u043d\u044b\u0439 \u043a\u043b\u0430\u0441\u0441: T - \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440 \u0442\u0438\u043f\u0430<\/span>\n    <\/span>static<\/span> <\/span>class<\/span> Box<\/span><<\/span>T<\/span>><\/span> {<\/span>\n        <\/span>private<\/span> <\/span>final<\/span> <\/span>T<\/span> <\/span>value<\/span>;<\/span>\n        <\/span>Box<\/span>(<\/span>T<\/span> <\/span>value<\/span>) { <\/span>this<\/span>.<\/span>value<\/span> <\/span>=<\/span> <\/span>value<\/span>; }<\/span>\n        <\/span>T<\/span> <\/span>get<\/span>() { <\/span>return<\/span> <\/span>value<\/span>; }<\/span>\n        <\/span><<\/span>R<\/span>><\/span> <\/span>Box<\/span><<\/span>R<\/span>><\/span> <\/span>map<\/span>(<\/span>Function<\/span><?<\/span> <\/span>super<\/span> <\/span>T<\/span>, <\/span>?<\/span> <\/span>extends<\/span> <\/span>R<\/span>><\/span> <\/span>f<\/span>) {<\/span>\n            <\/span>return<\/span> <\/span>new<\/span> <\/span>Box<\/span><><\/span>(<\/span>f<\/span>.<\/span>apply<\/span>(<\/span>value<\/span>));<\/span>\n        }<\/span>\n    }<\/span>\n\n    <\/span>\/\/ \u041e\u0431\u043e\u0431\u0449\u0435\u043d\u043d\u044b\u0439 \u043c\u0435\u0442\u043e\u0434: \u0441\u0432\u043e\u0439 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440 <T> \u043f\u0435\u0440\u0435\u0434 \u0442\u0438\u043f\u043e\u043c \u0440\u0435\u0437\u0443\u043b\u044c\u0442\u0430\u0442\u0430<\/span>\n    <\/span>static<\/span> <\/span><<\/span>T<\/span>><\/span> <\/span>T<\/span> <\/span>firstOrDefault<\/span>(<\/span>List<\/span><<\/span>T<\/span>><\/span> <\/span>list<\/span>, <\/span>T<\/span> <\/span>fallback<\/span>) {<\/span>\n        <\/span>return<\/span> <\/span>list<\/span>.<\/span>isEmpty<\/span>() <\/span>?<\/span> <\/span>fallback<\/span> : <\/span>list<\/span>.<\/span>get<\/span>(<\/span>0<\/span>);<\/span>\n    }<\/span>\n\n    <\/span>\/\/ \u041e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u0435 \u0441\u0432\u0435\u0440\u0445\u0443: T \u0443\u043c\u0435\u0435\u0442 \u0441\u0440\u0430\u0432\u043d\u0438\u0432\u0430\u0442\u044c\u0441\u044f \u0441\u0430\u043c \u0441 \u0441\u043e\u0431\u043e\u0439<\/span>\n    <\/span>static<\/span> <\/span><<\/span>T<\/span> <\/span>extends<\/span> <\/span>Comparable<\/span><?<\/span> <\/span>super<\/span> <\/span>T<\/span>>><\/span> <\/span>T<\/span> <\/span>max<\/span>(<\/span>List<\/span><<\/span>T<\/span>><\/span> <\/span>list<\/span>) {<\/span>\n        <\/span>T<\/span> <\/span>best<\/span> <\/span>=<\/span> <\/span>list<\/span>.<\/span>get<\/span>(<\/span>0<\/span>);<\/span>\n        <\/span>for<\/span> (<\/span>T<\/span> <\/span>x<\/span> : <\/span>list<\/span>) {<\/span>\n            <\/span>if<\/span> (<\/span>x<\/span>.<\/span>compareTo<\/span>(<\/span>best<\/span>) <\/span>><\/span> <\/span>0<\/span>) <\/span>best<\/span> <\/span>=<\/span> <\/span>x<\/span>;<\/span>\n        }<\/span>\n        <\/span>return<\/span> <\/span>best<\/span>;<\/span>\n    }<\/span>\n\n    <\/span>public<\/span> <\/span>static<\/span> <\/span>void<\/span> <\/span>main<\/span>(<\/span>String<\/span>[]<\/span> <\/span>args<\/span>) {<\/span>\n        <\/span>Box<\/span><<\/span>String<\/span>><\/span> <\/span>box<\/span> <\/span>=<\/span> <\/span>new<\/span> <\/span>Box<\/span><><\/span>(<\/span>\"generics\"<\/span>);<\/span>\n        <\/span>String<\/span> <\/span>s<\/span> <\/span>=<\/span> <\/span>box<\/span>.<\/span>get<\/span>();                       <\/span>\/\/ \u0431\u0435\u0437 \u043f\u0440\u0438\u0432\u0435\u0434\u0435\u043d\u0438\u044f<\/span>\n        <\/span>Box<\/span><<\/span>Integer<\/span>><\/span> <\/span>len<\/span> <\/span>=<\/span> <\/span>box<\/span>.<\/span>map<\/span>(<\/span>String<\/span>::<\/span>length<\/span>);<\/span>\n        <\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>s<\/span> <\/span>+<\/span> <\/span>\" -> \"<\/span> <\/span>+<\/span> <\/span>len<\/span>.<\/span>get<\/span>());<\/span>\n\n        <\/span>List<\/span><<\/span>String<\/span>><\/span> <\/span>empty<\/span> <\/span>=<\/span> <\/span>new<\/span> <\/span>ArrayList<\/span><><\/span>();<\/span>\n        <\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>firstOrDefault<\/span>(<\/span>empty<\/span>, <\/span>\"\u043d\u0435\u0442 \u0434\u0430\u043d\u043d\u044b\u0445\"<\/span>));<\/span>\n\n        <\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>max<\/span>(<\/span>List<\/span>.<\/span>of<\/span>(<\/span>3<\/span>, <\/span>17<\/span>, <\/span>5<\/span>)));<\/span>\n        <\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>max<\/span>(<\/span>List<\/span>.<\/span>of<\/span>(<\/span>\"\u0433\u0440\u0443\u0448\u0430\"<\/span>, <\/span>\"\u044f\u0431\u043b\u043e\u043a\u043e\"<\/span>, <\/span>\"\u0430\u043f\u0435\u043b\u044c\u0441\u0438\u043d\"<\/span>)));<\/span>\n    }<\/span>\n}<\/span><\/code><\/pre>\n
    \u0412 \u043a\u043e\u043d\u0441\u043e\u043b\u0438 \u0431\u0443\u0434\u0435\u0442:<\/p>\n
    generics -> 8\n\u043d\u0435\u0442 \u0434\u0430\u043d\u043d\u044b\u0445\n17\n\u044f\u0431\u043b\u043e\u043a\u043e\n<\/code><\/pre>\n
    \u0420\u0430\u0437\u0431\u043e\u0440 \u043f\u043e \u0447\u0430\u0441\u0442\u044f\u043c:<\/p>\n