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Java Reflection API

Java Reflection API

Java Reflection API is a process of modifying or retrieve metadata of a class at run time.

The java.lang.Class class provides methods that can be used to get metadata and change the run time behavior of a class.

The java.lang and java.lang.reflect packages are providing classes for java reflection.

The Java Reflection API is using mainly as follows.

  1. IDE Development (Example: Eclipse, Myeclipse, Netbeans etc…)
  2. Testing Tools
  3. Debugger Tools

How to create Object of java.lang.Class?

  • Java.lang.Class provides methods to get metadata at a class runtime.
  • Java.lang.Class provides methods to change the runtime behavior of the class.

There are 3 ways to create the Instance of the Class class

  1. forName() method of Class class
  2. getClass() method of Object class
  3. the .class syntax

forName() method of Class class

  • It is used to load the Class dynamically
  • It retruns instance of the Class
  • It should be used, if we know the fully qaulified class name
  • It can not be used for primitive types

Example :

package com.samples;

public class NTutorial{

}

package com.samples;

public class Tutorial{

public static void main(String args[]) throws ClassNotFoundException{

Class c=Class.forName("com.samples.NTutorial");

System.out.println("Class name:"+c.getName());

}

}

Output

Class name:com.samples.NTutorial

getClass() method of Object class

  • It returns the instance of Class class.
  • It should be used if you know the type.
  • It can be used with primitives.

Example :

package com.samples;

public class NTutorial{

}

package com.samples;

public class Tutorial{

public void display(Object obj){

Class cls=obj.getClass();

System.out.println("Class Name:"+cls.getName());

}

public static void main(String args[]) {

NTutorial nt=new NTutorial();

Tutorial t=new Tutorial();

t.display(nt);

}
}

Output

Class Name: NTutorial

the .class syntax

  • It can be used like appending “.class” to type as follows in the example
  • It can be used for primitive data type also.

Example :

public class Tutorial{

public static void main(String args[]) {

Class c1=boolean.class;

Class c2=int.class;

Class c3=char.class;

Class c4=double.class;

Class c5=Tutorial.class;

System.out.println(c1.getName());

System.out.println(c2.getName());

System.out.println(c3.getName());

System.out.println(c4.getName());

System.out.println(c5.getName());

 

}
}

Output

boolean
int
char
double
Tutorial
Narayanaswamy

Hello! I am Narayanaswamy founder and admin of narayanatutorial.com. I have been working in IT industry more than 7 years. NarayanaTutorial is my web technologies blog. My specialties are Java / J2EE, Spring, Hibernate, Struts, Webservices, PHP, Oracle, MySQL, SQLServer, Web Hosting and Website Development.

I am a self learner and passionate about training and writing. I am always trying my best to share my knowledge through my blog.

The Author

Narayanaswamy

Narayanaswamy

Hello! I am Narayanaswamy founder and admin of narayanatutorial.com. I have been working in IT industry more than 7 years. NarayanaTutorial is my web technologies blog. My specialties are Java / J2EE, Spring, Hibernate, Struts, Webservices, PHP, Oracle, MySQL, SQLServer, Web Hosting and Website Development. I am a self learner and passionate about training and writing. I am always trying my best to share my knowledge through my blog.

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