how to write an exception class java code example

Example 1: what is exception in java

In java exception is an object. Exceptions are created when an abnormal 
situations are arised in our program. Exceptions can be created by JVM or 
by our application code. All Exception classes are defined in java.lang. 
In otherwords we can say Exception as run time error.

Example 2: exception handling in java example

public class Exception8 {
public static void main(String[]args)
{
   fun1();
   fun2();
}
static void fun1()
{
   	fun3();
}
static void fun2()
{
     	fun3();
}
static void fun3()
{
	try {
	System.out.println(20/0);
	}
	catch(ArithmeticException e)
	{
		System.out.println("Zero divison ");
	}
}
}

Example 3: exception java

1.Unchecked: occurs during run time
2.Checked Exceptions:occurs during the compile time. 
needs to be handled IMMEDIATELY
Exception handling: try & catch: blocks, used for handling the exception 
 
throws keyword is used within the method signature 
disadvantage is: throws keyword whoever calls the method 
will have to handle the exception again but with 
try/catch you handle once. Try/catch is better way to handle it 
in utility class. Next time you call method you don’t get any exceptions
 
most common Exception like NullPointerExceptio, 
ArrayIndexOutOfBound, ClassNotFoundException, IOException.
are unchecked and they are descended from java.lang.RuntimeException
In Selenium: nosuchelement, nostaleexception, nosuchaframe 
In SQL: SQL exception