Applications for Java generics

First, generic type

1  Packagegenerics;2 /**3 * Generic class, Format: public class name < generic type 1, ...>4  * @authorZHONGFG5 * @date 2015-06-166  * @param<T>7  */8 classStudent<t> {9     Ten     PrivateT num; One  A      PublicT Getnum () { -         returnnum; -     } the  -      Public voidsetnum (T num) { -          This. num =num; -     } +      - } +  A  Public classGenericsclass { at      Public Static voidMain (string[] args) { -          -student<string> S1 =NewStudent<string>(); -S1.setnum ("001"); -String NUM1 =s1.getnum (); - System.out.println (NUM1); in          -System.out.println ("----------------"); to          +student<integer> s2 =NewStudent<integer>(); -S2.setnum (2); the         intnum2 =s2.getnum (); * System.out.println (num2); $     }Panax Notoginseng}

Ii. generic methods

1  Packagegenerics;2 /**3 * Generic method, public < generic type > return value method Name (generic type)4  * @authorZHONGFG5 * @date 2015-06-166  */7 classActor {8     9      Public<T>voidShow (T t) {Ten          One System.out.println (t); A     } -      - } the  -  Public classGenericsmethod { -  -      Public Static voidMain (string[] args) { +          -Actor A =NewActor (); +A.show ("Angelababy"); AA.show (26); at     } -}

Three, generic interface

1  Packagegenerics;2 /**3 * Generic class, Format: public interface interface name < generic type 1, ...>4  * @authorZHONGFG5 * @date 2015-06-166  * @param<T>7  */8 InterfacePerson<t> {9 Ten      Public Abstract voidShow (T t); One } A  - classPersonimpl<t>ImplementsPerson<t> { -  the @Override -      Public voidShow (T t) { -         //TODO auto-generated Method Stub - System.out.println (t); +     } - } +  A  Public classGenericsinterface { at      Public Static voidMain (string[] args) { -          -person<string> P1 =NewPersonimpl<string>(); -P1.show ("Huang Xiaoming"); -          -person<integer> P2 =NewPersonimpl<integer>(); inP2.show (38); -     } to}

Four, generic high-level wildcard characters

1  Packagegenerics;2 3 Importjava.util.ArrayList;4 Importjava.util.Collection;5 6 /**7 * Generic Advanced (wildcard character)8 *? : Any type, if not explicitly specified, is an object or any Java class.9 *? Extends e: down qualification, E and its subclassesTen * Super E: Limit up, E and its parent class One  * @authorZHONGFG A * @date 2015-06-16 -  */ - classAnimal { the      - } -  - classDogextendsAnimal { +      - } +  A classCatextendsAnimal { at      - } -  -  Public classGenericswildcard { -      Public Static voidMain (string[] args) { -          in         //when a generic is clearly specified, it must be consistent before and after -collection<object> C1 =NewArraylist<object>(); to //collection<object> c2 = new arraylist<animal> (); error, front and back type inconsistent + //collection<object> C3 = New Arraylist<dog> (); ibid. - //collection<object> C4 = new arraylist<cat> (); ibid. the          *         //? indicates that any type is possible $collection<?> c5 =NewArraylist<object>();Panax Notoginsengcollection<?> C6 =NewArraylist<animal>(); -Collection<?> c7 =NewArraylist<dog>(); thecollection<?> C8 =NewArraylist<cat>(); +          A         //? Extends e: down qualification, E and its subclasses the //Collection< extends animal> C9 = new arraylist<object> (); error, Object not Animal subclass +collection<?extendsAnimal> C10 =NewArraylist<animal>(); -collection<?extendsAnimal> C11 =NewArraylist<dog>(); $collection<?extendsAnimal> C12 =NewArraylist<cat>(); $          -         //? Super E: Limit up, E and its parent class -collection<?SuperAnimal> C13 =NewArraylist<object>();  thecollection<?SuperAnimal> C14 =NewArraylist<animal>(); - //collection< Super animal> C15 = new arraylist<dog> (); error, Dog is not Animal and above typeWuyi //collection< Super animal> C16 = new arraylist<cat> (); Ibid . the     } -}

Applications for Java generics