Modifiers keyword used 

In java modifiers are keyword which are used to change the current definition of respected element. There are two categories of Java Modifiers

o   Access Modifier

o   Non-Access Modifier.

        modifiers java Exception Keywords

Access Modifier

Those modifiers which showing the scope of the element are known as Access Modifier. There are four types of Access Modifier.

  o   Default: It’s scope is within respected package except methods and data members of super class

  o   Public: it’s scope is within all over the packages, classes, interfaces etc.

  o   Private: it’s scope is within class 

  o   Protected: It’s scope is within respected package

Non-Access Modifier

Those modifiers which are but definition scope but change the functionality of the element are known as Non-Access Modifiers. Following are the type of Non-Access Modifier

  o   Static: used for create method and variable static

  o   Final: used for create class, method and variable final

  o   Abstract: used for creating abstract class and abstract method

  o   Synchronized: used for threads

  o   Volatile:  used for threads.

modifiers java Exception Keywords

Access Modifier	within class	within package	outside package by subclass only	outside package
Private	Y	N	N	N
Default	Y	Y	N	N
Protected	Y	Y	Y	N
Public	Y	Y	Y	Y

  Exception Handling

Exception handling is most powerful mechanism in java to control the exception which are occurs during program execution. Basically exception is one kind of interrupt which disturb the flow of program and exception handling remove these disturbances and maintain the flow of the programs.

Types of exception

There are three types of exception in which are the following Java:

  o   Checked Exception: those exceptions which are checked at compile time are known as Checked Exceptions. In other words, the compiler for fully say that to compile this piece of code you must enclosed this piece of code within any exception handling tools. Some of possible checked exceptions are listed below

1.       IOException

2.       SQLException

3.       DataAccessException

4.       ClassNotFoundException

5.       InvocationTargetException

6.       MalformedURLException

  o   Un-Checked Exception: those exceptions which are checked at runtime are known as Un Checked Exceptions. These exceptions are caused due to bad programming or poor programming. these exceptions are occurring when user interacting with your application, it may be caused of wrong inputs or invalid data etc. some of possible Un-Checked exceptions are listed below:

1.       NullPointerException

2.       ArrayIndexOutOfBoundsException

3.       ArithmeticException

4.       IllegalArgumentException

5.       NumberFormatException

  o   Error: when the expected outcome is different than it is known as error. So, in programming mostly errors are uncovering because we don’t know the occurring of errors.  Error is not an exception. When your programs are failed to give expected result this is error.

       Java Exception Handling Keywords

In Java there are five keywords are used for Checked and Un-Checked exception handling

  o   try

  o   catch

  o   finally

  o   throw

  o   throws

modifiers java Exception Keywords

       Try Catch block

when you write any piece of program and you think that their might be a chances of error occurring then to prevent this type of errors you have to use try catch block. The try block will execute your program, if any exception occur the catch block will catch that exception and throw it at runtime.

Example without try catch block

In above example the JVM first check any exception occur or not? If occur, then it checks any exception handler is available or not? If no any exception handler is available then JVM will handle its own ways, otherwise the flow of the program will be maintained by the respected exception handler. Now as we see on above image that exception will occur at line number five, in above example we divide 10 by 0 so in programing division by zero is not perform that’s why it’s trough’s the runtime exception and stop the execution of the program. 

Example with try catch block

modifiers java Exception Keywords

Now in above example we enclosed the ambiguity piece of code into try catch block, if there is any exception then catch block will catch the exception. As we see the exception is occurred but flow of program is not stop because of try catch exception handler.modifiers java Exception Keywords

You can use multiple catch block for example if you have a doubt that there may be an Arithmetic Exception will occur or may be an Array Outs of Bounds exception will occur then you can write multiple catch blocks surrounded by try block

try{

                // code for execution

} catch (ArithmeticException e) {

                // message when exception occur

} catch (ArrayOutOfBoundsException e) {

                // message when exception occur

}

Finally, block

Finally, block is actually not handling the exception. This block always executes either the exception occurs or not. This block is mainly used when you want to close data base connection or you want to leave a message that user always get this message. So, to handle these type of thing the finally block will execute

Example

modifiers java Exception Keywords

Now in above example as we notice the finally block is executing either any exception occurs or not. Now in each try block you can put more than one catch block but finally block will be used only once.

        Throw Exception

In java the throw keyword is an explicitly throw an exception for example if we have any piece of code and we already know that in this piece of code the chances of exception are more then we have to use throw exception.

Example

modifiers java Exception Keywords

Now in above program it generates a throw exception and stop the execution of the program

Throws Exception

In java the throws keyword is used for exception handling, this throws exception handling is used for to handle the check exception. This exception handler is helps the programmer to handle the normal flow of the program after any exception occur. If any unchecked exception is occurred than it’s your fault and you have to control it and throws exception handler is not responsible for it.

Example

modifiers java Exception Keywords