Input and Output Operations and File Handing in Java


Input Output Operations and File Handing in Java

i) Input and Output Operations

ii) File Handling in Java

iii) Exception Handling in Java
--------------------------------
i) Input and Output Operations
There three ways available for reading input.

a) Scanner

b) DataInputStream

c) BufferedReader
------------------------------
Using java.util.Scanner is the easier way and it includes many methods to check input is valid to read.

Read Input Example:
public static void main (String [] args){

Scanner scan = new Scanner(System.in); //System.in is an input stream
   
System.out.println("Enter Your Name");
String name = scan.nextLine();
System.out.println("You are Name is "+name);
   
System.out.println("Enter Your City");
String city = scan.next();
System.out.println("Your City is "+ city);
   
System.out.println("Enter a Number");
int num = scan.nextInt();
System.out.println("Your Number is "+num);
   
System.out.println("Enter a Mobile Number");
long num2 = scan.nextLong();
System.out.println("Your Mobile Number is "+num2);
       
System.out.println("Enter a Value");
double num3 = scan.nextDouble();
System.out.println("Your Value is "+num3);
   
System.out.println("Enter a Character");
char a = scan.next().charAt(0);
System.out.println("Your Char is "+a);
   
System.out.println("Enter a Value");
boolean val = scan.nextBoolean();
System.out.println("Your Value is "+val);


scan.close();
--------------------------------------------------
Display Output on the Console
int a=10, b=20;
System.out.println("Welcome to Selenium");//Welcome to Selenium
System.out.println("Value b is "+b); //Value b is 20
System.out.println("Value a is "+a + " Value b is "+b); //Value a is 10 Value b is 20
--------------------------------
ii) File Handling in Java
Using File Class we can handle Computer files.

Examples

1) Create a Folder
public static void main (String [] args){
File fileObject = new File("C:/Users/gcreddy/Desktop/Selenium");
fileObject.mkdir();
}   

2) Check the existence of Selenium Folder.
public static void main (String [] args){
File fileObject = new File("C:/Users/gcreddy/Desktop/Selenium");
boolean a = fileObject.exists();
       
if (a == true){
System.out.println("Folder Exists");
}
else {
System.out.println("Folder Not Exists");
}
}       
-------------------------------------------------
3) Delete a Folder
public static void main (String [] args){
File fileObject = new File("C:/Users/gcreddy/Desktop/Selenium");
fileObject.delete();
}       
-------------------------------------
4) Create a Text File
public static void main (String [] args) throws IOException{
File fileObject = new File("C:/Users/gcreddy/Desktop/UFT2.xls");
fileObject.createNewFile();
}       

5) Delete a Text File
public static void main (String [] args) throws IOException{
File fileObject = new File("C:/Users/gcreddy/Desktop/UFT.txt");
fileObject.delete();
}       
--------------------------------
iii) Exception Handling in Java
> An exception is an event, it occurs during execution of a program, when normal execution of the program is interrupted.

> Exception handling is mechanism to handle exceptions.

Common scenarios where exceptions may occurs
1) Scenario where Arithmeticexception occursIf we divide any number by Zero then Arithmeticexception occurs

Ex:
int a =10/0;
--------------------------
2) Scenario where NullPointerexception occurs.
if we have no value in any variable, performing any operation by the variable.

Ex:

String s =null;

System.out.pritln(s.length()); //NullPointerexception
--------------------------
3) Scenario where NumberFormatException occurs
The wrong formatting of any value.

Ex:

String s = "abc";
int a = Integer.parseInt(s);
System.out.println(a);//NumberFormatException

--------------------------

// Convert data from String type to Integer

public static void main (String [] args) {

Scanner scan = new Scanner(System.in);

System.out.println("Read two Numbers");
String s1= scan.nextLine();
String s2= scan.nextLine();

int a = Integer.parseInt(s1);
int b = Integer.parseInt(s2);
System.out.println(a+b);

scan.close();
---------------------------
4) Scenario where ArrayIndexOutOfBounds exception occurs.
if we insert any value in the worng index.

Ex:
int [] a = new int [5];
a[100] = 123;
System.out.println(a[100]); ArrayIndexOutOfBounds
----------------------------
Example:
public static void main (String [] args) {
int a =10;
int b = 0;
   
int result = a/b;
System.out.println(result);
System.out.println("Hello Java");
System.out.println("Hello Selenium");
}
----------------------------
Use try catch block
Syntax:

try{
Statements
-----
------
}
catch (Exception name){
Exception handling code
}
-------------------------
Example:
public static void main (String [] args) {
int a =10;
int b = 0;
   
try
{
int result = a/b;
System.out.println(result);
}
catch (ArithmeticException e){
System.out.println("Divided by Zero Error");   
}
System.out.println("Hello Java");
System.out.println("Hello Selenium");
}
-----------------------------
// Handling multiple exceptions
public static void main (String [] args) {
int a =10;
int b = 0;
   
int abc [] = new int[4];
   
try
{
int result = a/b;
System.out.println(result);
}
catch (ArithmeticException e1){
System.out.println("Divided by Zero Error");   
}

System.out.println("Hello Java");
   
try
{
abc[30]=200;
System.out.println(abc[30]);   
}
catch (ArrayIndexOutOfBoundsException e2){
System.out.println("Array Index Out of Bounds Error");
}

System.out.println("Hello Selenium");
}
--------------------------------

3 comments:

Hi Sir,

In exceptions 3rd Scenario "Where NumberFormatException occurs" Example we have to print 'a' value

System.out.println(y); (Incorrect)

System.out.println(a);

Thank you

Hi Sir,
This is Abhay.I have a doubt on build-in methods.How do we know this build in(Fileobject.mkdir()) method only we should use in particular place while create folder or files in system?
Can you please explain on this.

Post a Comment