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•     What is Exception handling in java?
•      User defined exception or Guide Lines for user defined exceptions

     In order to develop user defined Exception Handling based applications, as a programmer, 

   we come across three stages they are.

    

      1)     User defined Exception sub classes

2)     User defined General / Common classes

3)     User defined Specific Classes

      For Example:

      1)  Development of user defined Exception sub classes:

                    Example:

                         Develop a User defined exception subclass for detailing with negative salary of an 

                        employee

//NsalException.java

 Package javajavax.lang;

 Public class NsalException extends Exception{

    Public NsalException(String s) { 

     Super(s);

    }

}//NsalException-------------user defined exception subclass

        Develop a user defined exception subclass for complimenting the employee when whose 

       salary is positive

     //PsalException.java

     Package javajavax.lang;

     Public class PsalException extends RuntimeException {

     Public PsalException(String s) {

      Super(s);

       }

   } 

   Compile the above packages

   

           C:\> javac –d . NsalException.java

           C:\> javac –d . PsalException.java

    2) Development of User defined General Classes:

           User defined general class makes use of user defined Exception sub class

// write a java program for developing user defined general class for checking 

all the salary of all employees of all organization.

//Emp.java

package org.igate;

import javajavax.lang.NsalException;

import javajavax.lang.PsalException;

public class Emp{

publicvoid decidesal(String s)throws NsalException,PsalException,

NumberFormatException

{

     int sal=Integer.parseInt(s);

     if(sal<=0){

      NsalException no=new NsalException(“Invalid Salary”);

       }

      else

     {

      PsalException po=new PsalException(“Valid Salary”);

      Return(po);

     }

  }

 }

       }

       Compile the above Package as

       C:\> javac –d .Emp.java

    Here org.igate.Emp is comes under defined general / common class. We can be used by 

   many employees to check their salary.

   3) Development of User defined Specified Class:

        This development is used by individual programmer and this class makes use of user 

        defined general classes and user defined Exception sub classes

  

         //Write a java program which will develop user defined specific class

        //(XEmp) for checking the salary whether they are valid or invalid.

//XEmp.java

import org.igate.Emp;

import javajavax.lang.NsalException;

import javajavax.lang.PsalException;

public class XEmp{

 public static void main(String args[]){

       try{

          String sal=args[0];

          Emp eo=new Emp();

eo.decidesal(sal);

 }

Catch(NsalException no){

    System.out.println(“Do not  enter negative salary”);

    }

Catch(PsalException po){

    System.out.println(“Ok try to improve yours salary”);

    }

Catch(NumberFormatException nfe){

   System.out.println(“PLZ enter numerical values”);

    }

Catch(ArrayIndexOutOfBoundsException nfe){

   System.out.println(“Enter the Employees salary from command prompt”);

    }

   Catch(Exceptione){

     System.out.println(e);

   }

  }

}

Ouput:

1)     C:\> javac XEmp.java

         C:\> java XEmp 9000

               Valid salary

               Ok try to improve yours salary //user defined exception message

2)       C:\> javac XEmp.java

          C:\> java XEmp -3

              Invalid salary

             Do not enter negative salary  // user defined exception message

3)       C:\> javac XEmp.java

          C:\> java XEmp

          Enter the Employees salary from command prompt

                                            // handling by predefined process or it is due to 

                                          // pre defined exception