Checked Vs Unchecked Exception in Java

Last Updated: 30 September, 2023

An exception is an unexpected event that occurs during program execution and affects the current flow of the program execution, which can cause the program to terminate abnormally.

In Java, exceptions have been categorized into two types, and they are as follows:

✅ Checked Exception

✅ Unchecked Exception

Checked Exception

A checked exception is one that the compiler examines during the Java program's compilation process to determine whether the programmer has handled it or not. If it is not handled, the compiler displays a compilation error using built-in classes.

The checked exception is also known as a compile-time exception.

In Java, checked exceptions are handled using either try-catch blocks or a throws keyword in the method declaration.

There are some built-in classes used to handle checked exceptions in Java:

• IOException
• FileNotFoundException
• ClassNotFoundException
• SQLException
• DataAccessException
• InvocationTargetException, etc.

All the checked exception classes are direct child classes of the Exception class.

Let's look at an example of a checked exception below.

Checked Exception Example

import java.io.File; import java.io.FileReader; public class CheckedExceptionExample { public static void main(String[] args) { File f_ref = new File("C:\\javabytechie\\java\\examples\\StudentReport.txt"); try { FileReader fr = new FileReader(f_ref); } catch (Exception e) { System.out.println(e); } } }

Output

java.io.FileNotFoundException: C:\javabytechie\java\examples\StudentReport.txt (The system cannot find the path specified)

Unchecked Exception

An unchecked exception is an exception that occurs at the time of program execution. Unchecked exceptions are typically the result of bugs like logic mistakes, improper resource usage, etc. At the time of compilation, the compiler does not catch the unchecked exceptions.

The unchecked exception is also known as a runtime exception.

There are some built-in classes used to handle unchecked exceptions in Java:

• NullPointerException
• ArithmeticException
• NumberFormatException
• ArrayIndexOutOfBoundsException
• StringIndexOutOfBoundsException, etc.

All the unchecked exception classes are children of the RuntimeException class, which is a child class of the Exception class.

Let's look at an example of a checked exception below.

Unchecked Exception Example

public class UncheckedExceptionExample { public static void main(String[] args) { String studentName = null; int marks[] = { 10, 20, 30, 40, 50 }; System.out.println(studentName.length()); // NullPointerException System.out.println(marks[6]); // ArrayIndexOutOfBoundsException int number = Integer.parseInt(studentName); // NumberFormatException } }

Output

Exception in thread "main" java.lang.NullPointerException at com.javabytechie.exceptionhandling.UncheckedExceptionExample.main(UncheckedExceptionExample.java:9)

Checked Vs Unchecked Exception in Java