Java SE-reflect

Test class

 Package  Testreflect;  /**  * @ Package testreflect * @ classname: HELLO * @ Description: Todo ()*  @ Author  Andy * @ date 2013-5-31 09:59:29 AM  */  Public   Class  Hello {  Public  String name;  Private   Int Id = 1;  Public  Hello (){}  Public Hello (string name, Int  ID ){  This . Name = Name;  This . ID = ID ;}  Public  String GetUserName (){  Return "123" ;} Public  String getname (){  Return  Name ;}  Public   Void  Setname (string name ){  This . Name = Name ;}  Public   Int  GETID (){  Return  ID ;}  Public  Void Setid ( Int  ID ){  This . ID = ID ;}} 

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Three methods to obtain the object of a class or object runtime class

 Package  Testreflect;  /**  * @ Package testreflect * @ classname: instancingclass * @ Description: Todo (three methods for obtaining the class object during running of a class or object )*  @ Author  Andy * @ date 2013-5-31 09:59:05 AM  */ Public   Class Instancingclass <t> {  Public   Static   Void Main (string [] ARGs) Throws  Classnotfoundexception {  //  First Class <Hello> classtype1 = hello. Class  ;  //  Second Class <?> Classtype2 = Class. forname ("testreflect. Hello" );  //  Third Hello = New  Hello (); Class <? Extends Hello> classtype3 = Hello. getclass (); system. Out. println (classtype1 + "\ N" + classtype2 + "\ n" + classtype3 + "\ n" ); System. Out. println (classtype1.getname () + "\ N" + classtype2.getname () + "\ n" + classtype3.getname () + "\ n" ); System. Out. println (classtype1.getsimplename () + "\ N" + classtype2.getsimplename () + "\ n" + classtype3.getsimplename () + "\ n" );}} 

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Three methods for instantiating objects without the New Keyword

 Package  Testreflect;  Import  Java. Lang. Reflect. constructor;  Import  Java. Lang. Reflect. invocationtargetexception;  /**  * @ Package testreflect * @ classname: instancingobject * @ Description: Todo (three methods to instantiate an object without the New Keyword )*  @ Author Andy * @ date 2013-5-31 10:08:34 AM  */  Public   Class  Instancingobject {  Public   Static   Void Main (string [] ARGs) Throws  Instantiationexception, illegalaccessexception, nosuchmethodexception, securityexception, illegalargumentexception, invocationtargetexception {Hello hello0 = Hello. Class  . Newinstance (); Class <Hello> classtype = hello. Class  ;  //  When the constructor has no parameters, the first is equivalent to the second.  //  First Hello hello1 = (Hello) classtype. newinstance ();  //  Second Constructor <Hello> con = Classtype. getconstructor (); Hello hello2 = (Hello) con. newinstance ();  // Third Constructor <Hello> con2 = classtype. getconstructor ( New Class [] {string. Class , Int . Class  }); Hello hello3 = (Hello) con2.newinstance ( New Object [] {"123", 123 }); System. out. println (hello0.getusername (); system. out. println (hello1.getusername (); system. out. println (hello2.getusername (); system. out. println (hello3.getusername ());}} 

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Operations on fields through reflection

Package  Testreflect;  Import  Java. Lang. Reflect. accessibleobject;  Import  Java. Lang. Reflect. field;  /**  * @ Package testreflect * @ classname: accessfieldbyreflect * @ Description: Todo (operations on fields through reflection )*  @ Author  Andy * @ date 2013-5-31 10:48:13 AM  */  Public   Class  Accessfieldbyreflect { Public   Static   Void Main (string [] ARGs) Throws  Illegalargumentexception, illegalaccessexception, instantiationexception {hello = Hello. Class  . Newinstance (); field [] fields = Hello. getclass (). getdeclaredfields ();  //  Retrieve all fields through Traversal          For  (Field: fields ){  // System. Out. println (field );  System. Out. println (field. getname ();} system. Out. println ( "Before modification:" + Hello. getname (); system. Out. println ( "Before modification:" + Hello. GETID ());  For  (Field: fields ){  If ("ID" . Equals (field. getname ())){  //  Allow access to all private fields, methods, and constructor Elements Field. setaccessible ( True );  //  Field that can only be accessed Accessibleobject [] accessparam = {Field}; field. setaccessible (accessparam,  True  );  //  If the field is int, It is setint. If it is double, It is setdouble. Field. setint (hello, 123 );}  Else  {  //  The field is a string Field. Set (hello, "James" ) ;}} System. Out. println ( "Modified by reflection:" + Hello. GETID (); system. Out. println ( "Modified by reflection:" + Hello. getname ());}} 

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Operations on methods through reflection

 Package  Testreflect;  Import  Java. Lang. Reflect. accessibleobject;  Import  Java. Lang. Reflect. invocationtargetexception;  Import Java. Lang. Reflect. method;  /**  * @ Package testreflect * @ classname: accessmethodbyreflect * @ Description: Todo (operations on methods through reflection )*  @ Author  Andy * @ date 2013-5-31 11:25:39 AM  */  Public   Class  Accessmethodbyreflect {  Public   Static   Void Main (string [] ARGs) Throws Illegalargumentexception, illegalaccessexception, instantiationexception, invocationtargetexception, nosuchmethodexception, securityexception {hello = Hello. Class  . Newinstance (); method [] Methods = Hello. getclass (). getdeclaredmethods ();  //  Retrieve all fields through Traversal          For  (Method: Methods ){  //  System. Out. println (field ); System. Out. println (method. getname ();} system. Out. println ( "Before modification:" + Hello. getname (); system. Out. println ( "Before modification:" + Hello. GETID ());  For  (Method: Methods ){  If ("Setid" . Equals (method. getname ())){  //  Allow access to all private fields, methods, and constructor Elements Method. setaccessible ( True  ); //  Only allow access to the specified Method Accessibleobject [] accessparam = {Method}; method. setaccessible (accessparam,  True  );}  Else   If ("Setname" . Equals (method. getname () {method. Invoke (hello, "James" ) ;}} String OBJ = (String) Hello. getclass (). getdeclaredmethod ("getname" ). Invoke (Hello); system. Out. println ( "Returned value by reflecting the getname method:" +OBJ); system. Out. println ( "Modified by reflection:" + Hello. GETID (); system. Out. println ( "Modified by reflection:" + Hello. getname ());}} 

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Int returned by integer. type, that is, the native data class objects corresponding to them (all the packaging classes are like this ),

Integer. Class returns the corresponding class Object java. Lang. integer.