All computer programs must accept input and generate output. Java

Features a rich set of classes that represent everything from a general

Input or output stream to a sophisticated random-access file

File are used to store large amounts of data for a long period of time

Specially, random-access files are used to read from and write to any

Location in the file

Streams, on the other hand, merely refers to the flow of data.

It represents a connection to a communications channel. There are

Input streams, which direct data from outside world to the

Computer, and output streams, which direct data toward output

Devices, such as the computer screen or a file

The following are the classes in the java.i0 package:

 What are Random-Access Files?

The Random Access File Class provides standard file handling which

Allows opening, closing, reading, and writing files the general

Technique is to open a file by creating a new Random-access File object

With a filename as a parameter then read the file into an array of bytes

The byte array can then be manipulated and written back to the file

Random-access files are appropriate for "instant-access" application.

Practical application include: airline reservation systems, banking systems

POS systems, automated teller machines, etc.

An exception is an occurrence, usually some form of error, that happen

While a program is executing the normal flow of execution is disrupted

And transferred to code which can handle the exceptional condition

The exception mechanism is a lot cleaner than having to check an error

Value after every method call which could potentially fail

Java defines many different exception object some of these you must

Always handle in your code if you call a method that may throw the

Exception .others are generated by the system when something like

Allocation fail, an expression tries to divide by 0, a null is used

Inappropriately, and so no

Arithmetic Exception Cause by math errors such as division by zero

Array Index Out of Bounds Exception Cause by bad array indexes

Array Store Exception Cause when a program tries to store the wrong

Type of data in an array

File not found Exception Cause by an attempt to access a nonexistent file

IO Exception Cause by general I/O failures, such as inability

To read from a file

Null Pointer Exception Cause by referencing a null object

Number Format Exception Cause when a conversion between strings

And numbers fails

Out Of Memory Exception Cause when there is not enough memory to

Allocated a new object

Security Exception Cause when an applet tries to perform an action

Not allowed by the browser’s security setting

Stock Over Flow Exception Cause when the system runs out of stock space

String Index Out of Bounds Cause when a program attempts to access a

Exception

Nonexistent character position in string

Constructions: Throw able ( )

Throw able (String message)

Methods: Throw able Fill in Stack Track ( )

Void Print Stack Trace ( )

Void Print Stack Trace (print stream out)

String Get Message ( )

String to String ( )

Serious error in the java runtime system. You should never catch this type

Of exception and in a correct system they should , on the whole, not occur

The major exception to this is the Thread Death exception, which is a special

Case.

Normal errors that can occur during the execution of a program .

They include problems such as array bound errors and floating point.

Exception . These exceptions are usually handled by code block.

Encompasses all exceptions which can ordinarily happen at runtime.

Exception are generated in several ways, namely:

If a method or constructor is declared to throw an exception, them calling

that method or constructor may result in an exception of declared class or a

subclass. It is a compile-time error for a method body to throw , and not

catch, an exception that is not declared in the throws clause, unless it is a

Runtime exception.

int method ( ) throws IOexception {

…..

}

method ( ) ; // this can throw an exception

These exception can occur even through the offering piece of code does not

declared that it throws such an exception .Examples of these exceptions include:

Null pointer Exception, Array Index Out of Bound Exception , etc..

These exception can be thrown by a language statement or a method call;

The method executes a statement which throws the exception, and the method

Does not