Java Learning Note (61)-Reflection reflection

Reflective Reflection

Import Java. Lang. Reflect. Modifier;/ * * Reflection Reflection * Java.lang.Class Class * *public class Test01 {public static void main (string[] args) {String name ="Tom";Way one: Through the object GetClass () method//object of any class, there is a getclass () method//Can get the class object of the type of the current object.CLS= Name. GetClass();Showinfo (CLS);Mode two: Through the class forname () static method try {class Cls2=class. forname("com.itany.basejava.day37.Test01");Showinfo (CLS2);} catch (ClassNotFoundException e) {E. Printstacktrace();}//Way Three: Class Cls3=student by specifying classes. Class;Showinfo (CLS3);}//Gets information about the class object public static void Showinfo (classCLS) {System. out. println("The full name of the class:"+CLS. GetName());System. out. println("class name:"+CLS. Getsimplename());System. out. println("Owning package:"+CLS. Getpackage());System. out. println("is a local class:"+CLS. Islocalclass());System. out. println("Whether it is an interface:"+CLS. Isinterface());System. out. println("is an array:"+CLS. IsArray());System. out. println("is the base data type:"+CLS. Isprimitive());Gets the class object of its parent class, class Supercls =CLS. Getsuperclass();System. out. println("Parent class's full name:"+ SUPERCLS. GetName());Gets the modifier of the class int m =CLS. GetModifiers();System. out. println("modifier is:");if (Modifier. IsPublic(m)) {System. out. Print("Public");} if (Modifier. IsStatic(m)) {System. out. Print("Static");} if (Modifier. IsAbstract(m)) {System. out. Print("Abstract");} if (Modifier. IsFinal(m)) {System. out. Print("Final");} System. out. println("**************************************\n");}}

To instantiate an object by using reflection to access the construction method

Import Java.lang.reflect.constructor;import Java.lang.reflect.Method;/* * The object is instantiated through the reflection access construction method * Constructor class * / Public classTest03 { Public Static void Main(string[] args) throws Exception {//Create an object of the dog class        //Dog Dog1=new dog ("Rhubarb", 3, "male");        //Create a Class object of the dog classclass<dog> cls = Dog.class;/ * * Instantiate an object without a parameter constructor, both ways */        //1. Create an instance from the Newinstance () method of the Class object, only for creating objects by using the parameterless construction methodDog dog = (dog) cls.newinstance ();//Dog.show ();method = Cls.getdeclaredmethod ("Show");        Method.invoke (dog); System. out. println ("*************************\n");//2. Get the constructor method with null parameterConstructor C = Cls.getdeclaredconstructor ();        Dog dog2 = (dog) c.newinstance ();        Dog2.show (); System. out. println ("*************************\n");/ * Instantiate the object with the parameter construction method */Constructor C2 = Cls.getdeclaredconstructor (NewClass[] {string.class,int. class, String.class}); Dog Dog3 = (dog) c2.newinstance ("Little Yellow",2,"female"); Dog3.show ();/ * * Instantiate an object through a private-modified construction method */constructor<dog> C3 = Cls.getdeclaredconstructor (NewClass[] {string.class, string.class}); C3.setaccessible (true); Dog Dog4=c3.newinstance ("Big Yellow","Medium");    Dog4.show (); }}/ * * Animal Parent class * /Class Animal { PublicString name;intAge Public Animal() {System. out. println ("How to construct a parent class without a parameter"); } Public Animal(String name,intAge) { This. name = name; This. Age = Age; System. out. println ("constructor method with parameters in parent class"); } Public void Show() {System. out. println ("Show method in parent class"); }}/ * * Dog class, inherited from Animal */Class Dog extends Animal {String sex; Public Dog() {System. out. println ("constructor method for no arguments in subclasses"); } Public Dog(String name,intAge, String Sex) {System. out. println ("constructor method with parameters in subclasses"); }Private Dog(string name, string sex) {System. out. println ("Construction method with two parameters in subclasses"); }//Override the Show method in the parent class     Public void Show() {System. out. println ("Show methods in subclasses"); }}

Field class

Import Java.lang.reflect.field;import Java.lang.reflect.invocationtargetexception;import Java.lang.reflect.Method ;/ * * Field class */ Public classTest02 { Public Static void Main(string[] args) throws SecurityException, Nosuchfieldexception, IllegalArgumentException, ILLEGALACC Essexception, Nosuchmethodexception, invocationtargetexception {//Create an object of the student class, that is, the student objectStudent STU1 =NewStudent (); Student STU2 =NewStudent ();//Create a Student class object, which is the class object of the student classesClass cls = Student.class;/ * * Field property operation; */        //1. Gets all the attributes in the student class, including all the public adornments in this class and the parent class        //field[] fields = Cls.getfields ();        //2. Gets all the attributes in the student class, including any properties decorated by any modifier in this classfield[] fields = Cls.getdeclaredfields (); for(Field f:fields) {System. out. println (F.getname ());//System.out.println (f.tostring ());} System. out. println ("**********************\n");//3. Get the properties specified in the Student classField name = Cls.getfield ("Name"); Field grade = Cls.getdeclaredfield ("Grade"); Field sex = Cls.getsuperclass (). Getdeclaredfield ("Sex");//Assign a value to a property        //Stu1.name= "Tom";//directly through the object name. Property name AssignmentName.Set(STU1,"Alice");//Assign a value to the property of the specified objectSystem. out. println ("STU1 's name:"+ Name.Get(STU1));//Set property to accessible, that is, set access modifierGrade.setaccessible (true); Grade.Set(STU1,2);//Assignment for STU1 's private property gradeSystem. out. println ("STU1 's Grade:"+ grade.Get(STU1)); System. out. println ("*****************************************\n");/ * Method Operation */        //1. Get all the methods in the Student class        //method[] methods = Cls.getmethods ();Method[] Methods=cls.getdeclaredmethods (); for(Method m:methods) {System. out. println (M.getname ()); }//2. Get the method specified in the Student class        //stu1.calc (ten);Class[] args1={int. class,Double. class}; Method Calc=cls.getmethod ("Calc", ARGS1); Object[] args2={Ten,25.4};DoubleSum= (Double) Calc.invoke (STU1, ARGS2); System. out. println ("The sum of two counts is:"+sum);//Get the private adornment methodMethod Show=cls.getdeclaredmethod ("Show"); Show.setaccessible (true);//Do not detect access modifiersShow.invoke (STU2);//Call method}}/ * * Person class */Class Person { PublicString name;intAgePrivateString sex;protected DoubleHeight;}/ * * Student class, inherited from person */Class Student extends Person { Public intId//Study No.    Private intGrade//Grade numberString ClassName;//class name     Public Student(){    } Public int Getgrade() {returnGrade } Public void Setgrade(intGrade) { This. grade = grade; } Public int Calc(intNUM1,intNUM2) {returnNUM1 + num2; } Public Double Calc(intNUM1,DoubleNUM2) {returnNUM1 + num2; }Private void Show() {System. out. println ("Sixth row right number two people a bit 22222"); }}

Java Learning Note (61)-Reflection reflection