Reflection

Java Reflection is a process of examining or modifying the run time behavior of a class at run time.

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

The java.lang and java.lang.reflect packages provide classes for java reflection.

Where it is used

The Reflection API is mainly used in:

• IDE (Integrated Development Environment) e.g. Eclipse, MyEclipse, NetBeans etc.
• Debugger
• Test Tools etc.

How to get the object of Class class?

There are 3 ways to get the instance of Class class. They are as follows:

• forName() method of Class class
• getClass() method of Object class
• the .class syntax

1) forName() method of Class class

• is used to load the class dynamically.
• returns the instance of Class class.
• It should be used if you know the fully qualified name of class.This cannot be used for primitive types.

Let's see the simple example of forName() method.

1. class Simple{}  
2.   
3. class Test{  
4.  public static void main(String args[]){  
5.   Class c=Class.forName("Simple");  
6.   System.out.println(c.getName());  
7.  }  
8. }  

Output:Simple

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2) getClass() method of Object class

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

1. class Simple{}  
2.   
3. class Test{  
4.   void printName(Object obj){  
5.   Class c=obj.getClass();    
6.   System.out.println(c.getName());  
7.   }  
8.   public static void main(String args[]){  
9.    Simple s=new Simple();  
10.    
11.    Test t=new Test();  
12.    t.printName(s);  
13.  }  
14. }  
15.    

Output:Simple

---

3) The .class syntax

If a type is available but there is no instance then it is possible to obtain a Class by appending ".class" to the name of the type.It can be used for primitive data type also.

1. class Test{  
2.   public static void main(String args[]){  
3.    Class c = boolean.class;   
4.    System.out.println(c.getName());  
5.   
6.    Class c2 = Test.class;   
7.    System.out.println(c2.getName());  
8.  }  
9. }  

Output:boolean
       Test