Java Reflection API
Table of Contents
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.
- IDE Development (Example: Eclipse, Myeclipse, Netbeans etc…)
- Testing Tools
- 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
- forName() method of Class class
- getClass() method of Object class
- 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
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