What is an exception in java? handle exception in java| easy 12 example


What is an exception in java? handle exception in java

Java – exception. An exception (or extraordinary event) is a problem that occurs during the execution of a program. When an exception occurs, the normal flow of the program is interrupted and the program / application terminates abnormally, which is not recommended, therefore, these exceptions have to be controlled.

Types of exception to handle exception in java

There are Two type of exception

  • Checked Exception

Checked exception occur at compile time or generated by compiler.

  • Unchecked Exception

Unchecked exception occured at run time

What is an exception in java
Type of Exception

Checked and unchecked exception type

handle exception in java
handle exception in java
  • ArithmeticException

It is thrown when an exceptional condition has occurred in an arithmetic operation.

Class: Java.lang.ArithmeticException
This is the built-in-class present in the java.lang package. This exception occurs when the integer is divided by zero.

Example:

Class example 1
{
public static void main (String [] args[])
{
try{
int num1 = 30, num2 = 0;
int output = num1 / num2;
System.out.println (“Result:” + output);
}
Catch (ArithmeticException) {
System.out.println (“You should not divide a number by zero”);
}
}
}

Output

You should not divide a number by zero

Explanation: In the above example I divided an integer by a zero and because of this an arithmetic exception was thrown.

  • ArrayIndexOutOfBoundsException

It is thrown to indicate that an array has been accessed with an invalid index. The index is either negative or equal to or greater than the size of the array.

Class: Java.lang.ArrayIndexOutOfBoundsException
This exception occurs when you try to access an array index that does not exist. For example, if the array has only 5 elements and we are trying to display the 7th element it will throw an exception.

Example:


Class exception demo 2
{
public static void main (String [] args[])
{
try{
int a [] = new int [10];
Array contains only 10 elements
[11] = 4;
}
Catch (ArrayIndexOutOfBoundsException e) {
System.out.println (“ArrayIndexOutofBounds”);
}
}
}

Result

ArrayIndexOutofBounds

  • ClassNotFoundException

This exception is raised when we try to access a class whose definition is not found

Example

Package com.journaldev.exception;
Public class DataTest {
public static void main (String [] args) {
try {
Class.forName (“com.journaldev.MyInvisibleClass”);
ClassLoader.getSystemClassLoader () loadClass (“com.journaldev.MyInvisibleClass”).;
ClassLoader.getPlatformClassLoader () loadClass (“com.journaldev.MyInvisibleClass”).;
} Catch (ClassNotFoundException e) {
e.printStackTrace ();
}
}
}

Result

ClssNotFoundException in java
ClassNotFoundExcepion
  • FileNotFoundException

This exception is raised when a file is unreachable or does not open.

Example

Import java.io.BufferedReader;
Import java.io.File;
Import java.io.FileReader;
Import java.io.IOException;
Public class FileNotFoundExceptionExample {
Private static final string filename = “input.txt”;
public static void main (String [] args) {
Bufferreader rd = null;
try {
// Open the file for reading.
rd = new BufferedReader (new FileReader (new File (filename)));
// Read all the contents of the file.
String inputline = null;
While ((inputline = rd.readLine ())! = Null)
Println (inputLine);
}
Catch (before IOException) {
System.err.println (“An IOException was caught!”);
ex.printStackTrace ();
}
After all
// Close the file.
try {
rd.close ();
}
Catch (before IOException) {
System.err.println (“An IOException was caught!”);
ex.printStackTrace ();
}
}
}
}

OutPut

FileNotFoundException
FileNotFoundException
  • IOException

It is thrown when the input-output operation fails or is interrupted

Example

Import java.util. *;
Public class ScannerIOExceptionExample1 {
public static void main (String [] args) {
// create a new scanner with the specified string object
ScannerScan = new Scanner (“Hello World! Hello My Programming School”);
// print the line
System.out.println (“” + scan.nextLine ());
// check if there is an IO exception
System.out.println (“Exception output:” + scan.ioException ());
scan.close ();
} }

OutPut:

Hello World! Hello My Programming School Exception output: null

  • InterruptedException

It is thrown when a thread is waiting, sleeping, or processing something, and it is interrupted.

Example

Package com.javaguides.corejava;
Class childhread’s extension thread {
Public void run () {
try {
Thread.Sleep (1000);
} Catch (interrupted exception) {
System.err.println (“InterruptedException caught!”);
e.printStackTrace ();
}
}
}
Public class InterruptedExceptionExample {
Public static void main (String [] args) throws InterruptedException {
ChildThread childThread = new ChildThread ();
childThread.start ();
childThread.interrupt ();
}
}

Out Put:

IntrruptedException
IntrruptedException
  • NoSuchFieldException

It is thrown when a class does not contain a specified field (or variable)

  • NoSuchMethodException

It is thrown when using a method that is not found.

  • NullPointerException

This exception is raised when referring to members of a null object. Null represents nothing

Class: Java.lang.NullPointer Exception
Whenever a member is called with an “null” object, an object of this class is created.

Example

Class exception 2
{
public static void main (String [] args[])
{
try{
String str = null;
System.out.println (str.length ());
}
Catch (NullPointerException e) {
Println (“NullPointerException ..”);
}
}
}

Result

NullPointerException ..

Here, there is a length () function, which should be used on an object. However the string object str in the above example is null so it is not the object that caused the NullPointerException.

  • NumberFormatException

This exception is raised when a method cannot convert a string to a numeric format.

Class: Java.lang.NumberFormatException

This exception occurs when a string is parsed on any numeric variable.

For example, the statement int num = Integer.parseInt (“XYZ”); The numbers will throw a FormatException because the string “XYZ” cannot be parsed to int.

Example

Class ExceptionDemo3
{
public static void main (String [] args[])
{
try{
int num = Integer.parseInt (“XYZ”);
Println (number);
} Catch (numberFormatException e) {
System.out.println (“Number format exception occurred”);
}
}
}

Result

Number format exception occurred

  • Runtime Exception

This represents any exception that occurs during runtime.

Example

You can see above example of FileNotFoundException

  • StringIndexOutOfBoundsException

It is thrown by string class methods to indicate that the index is either negative by the size of the string

Class: Java.lang.StringIndexOutOfBoundsException

Whenever an index is not implemented in a string, an object of this class is created, which is not in the range.
Each character of a string object is stored in a special index starting at 0.
To get a character present in a particular index of a string we can use charAt (int), a method of java.lang.tring. Where the difference is the logic index.

Example

Class ExceptionDemo4
{
public static void main (String [] args[])
{
try{
String str = “beginbook”;
Println (str.length ()) ;;
char c = str.charAt (0);
c = str.charAt (40);
Println (c);
} Catch (StringIndexOutOfBoundsException e) {
Println (“StringIndexOutOfBoundsException !!”);
}
}
}

Result

StringIndexOutOfBoundsException !!

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The exception occurred because the referenced index was not present in the string.

What is an exception in java? handle exception in java

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