ClassNotFound & ClassNoDefFound

-> It is an exception. It is of type java.lang.Exception.
   where as It is an error. It is of type java.lang.Error.
-> It occurs when an application tries to load a class at run time which is not updated in the classpath.
   where as It occurs when java runtime system doesn’t find a class definition,which is present at compile time, but missing at run time.
-> It is thrown by the application itself. It is thrown by the methods like Class.forName(),
   loadClass() and findSystemClass().
   where as It is thrown by the Java Runtime System.
-> It occurs when classpath is not updated with required JAR files.
   where as It occurs when required class definition is missing at runtime.


**** ClassNotFoundException ***
Ex.

public class MainClass
{
    public static void main(String[] args)
    {
        try
        {
            Class.forName("oracle.jdbc.driver.OracleDriver");
        }catch (ClassNotFoundException e)
        {
            e.printStackTrace();
        }
    }
}

******** NoClassDefFoundError  *******
 Ex....
  class A
{
  // some code
}
public class B
{
    public static void main(String[] args)
    {
        A a = new A();
    }
}