Java Reflection API | Java.lang.Class

Ref:http://www.studytonight.com/java/reflection-api

Reflection API

Reflection means ability of a software to analyze itself. In Java, Reflection APIs provides facility to analyze and change runtime behavior of a class, at runtime

For Example, using reflection at the runtime can determine what method or modifiers a class supports

What is the reflect package?

Java.lang.reflect Package encapsulates serveral important interface and classes. These classes and interface define methods which is used for reflection

Class description

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Array allow you to dynamically created and manipulate arrays

Constructor gives info abt Constructor of a class

field provides info abt field

Method Procide Info Abt method

Modifier provide info abt class and member access Modifier

Proxy supports dynamic proxy classes

Java.lang.Class is another important class used in Reflection API

Uses of Reflection

1. Developing IDE
2. Debugging and Test Tools

3. Loading drivers and providing dynamic info

Disadvantages of Reflection

1. Low performance

2. Security risk

3. Violation of OOPs concept

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Reflection Class

Java.lang.Class

Class is a final class Injava.lang package which extends Object class. Instance of this class

Represents classes and interfaces in a running Java application. It is used to analyze and change dynamic behavior of a class at runtime

Some Important Methods of Java.lang.Class Class

This class defines several methods using which we can get info on methods, constructors, modifiers and members of a CLA SS at runtime

Forname ()

1. This method takes fully qualified name of the classes or nterfaces as its argument and return instance

of the class associated with it.

2. Static class<?> forname (String className)

Class Student{}class test{public static void Main (String args[]) {  class.forname("Student");  System.out.println (c.getname ()); }}
Output:student

GetConstructors () and Getdeclaredconstructors ()

1. GetConstructors () returns array of constructors object that represent all the public constructors of the invoking OBJEC T. This method is only returns public constructor. Getdeclaredconstructors () would return all constructors

Constructor GetConstructors (); Constructor getdeclaredconstructors ();

Example using GetConstructors () and Getdeclaredconstructors () method

Class C = class.forname ("Student");  c.getconstructors ();  for (int i=0; i< ct.length; i++)    {System.out.println (ct[i]);}  c.getdeclaredconstructors ();  for (int i=0;i< cdt.length;i++)    {System.out.println (cdt[i]);}
Output

  Public Student () public  Student ()  Student (java.lang.String)

GetMethods () and Getdeclaredmethods () GetFields () and Getdeclaredfields () Example using GetFields () and Getdeclaredfields () method

Java Reflection API | Java.lang.Class