What are different types of exceptions in Java?

Introduction

An exception is an event that occurs during the execution of a program that disrupts the normal flow of the program's instructions. In Java, exceptions are objects that describe an exceptional (error) condition that has occurred in a piece of code. They are used to handle errors and other exceptional events in programs written in the Java programming language.

Types of exceptions

There are two kinds of exceptions in Java:

Checked exceptions: These are the exceptions that are checked by the compiler at compile time. If a method throws a checked exception, then the caller of the method must either handle the exception or declare it in the throws clause.
Unchecked exceptions: These are the exceptions that are not checked by the compiler at compile time. They include runtime exceptions and errors.

Exception class hierarchy in Java

The exception class hierarchy in Java is as follows:

List of common unchecked exceptions in Java

Exception classes	Description
RuntimeException	This is the superclass of all unchecked exceptions.
NullPointerException:	This exception is raised when a null value is used where an object is required.
ArithmeticException	This exception is raised when an arithmetic operation fails.
ArrayIndexOutOfBoundsException	This exception is raised when an array index is out of bounds.
IllegalArgumentException	This exception is raised when an illegal argument is used.
IllegalStateException	This exception is raised when an illegal state is detected.
ConcurrentModificationException	This exception is raised when a collection is modified while it is being iterated over.

Errors in Java

Error classes	Description
OutOfMemoryError	This error is raised when the JVM runs out of memory.
StackOverflowError	This error is raised when a stack overflow occurs.
VirtualMachineError	This is the superclass of all errors that occur in the JVM.
AssertionError	This error is raised when an assertion fails.
NoClassDefFoundError	This error is raised when a class cannot be found.
LinkageError	This error is raised when a linkage problem occurs.
ExceptionInInitializerError:	This error is raised when an exception occurs in the static initializer of a class.

import java.io.IOException;
public class ExceptionExample {
    // Checked exception example
    public static void readDataFromFile() {
        try {
            // Simulating an IO operation that may throw IOException
            // Instead of throwing the exception, handle it gracefully
            throw new IOException("Failed to read data from file");
        } catch (IOException e) {
            System.out.println("IOException caught: " + e.getMessage());
            // Perform necessary error handling or recovery actions here
        }
    }
    // Unchecked exception example
    public static void divide(int a, int b) {
        try {
            // Simulating an arithmetic operation that may throw ArithmeticException
            if (b == 0) {
                throw new ArithmeticException("Division by zero");
            } else {
                int result = a / b;
                System.out.println("Result of division: " + result);
            }
        } catch (ArithmeticException e) {
            System.out.println("ArithmeticException caught: " + e.getMessage());
            // Perform necessary error handling or recovery actions here
        }
    }
    // Error example
    public static void causeOutOfMemoryError() {
        try {
            // Simulating an out of memory situation
            int[] array = new int[Integer.MAX_VALUE];
        } catch (OutOfMemoryError e) {
            System.out.println("OutOfMemoryError caught: " + e.getMessage());
            // Perform necessary error handling or recovery actions here
        }
    }
    public static void main(String[] args) {
        // Demonstrating checked exception handling
        readDataFromFile();
        // Demonstrating unchecked exception handling
        divide(10, 0); // This will cause an ArithmeticException
        // Demonstrating error handling
        causeOutOfMemoryError();
    }
}

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Exception class	Description
IOException	This exception is raised when an input/output operation fails
SQLException	This exception is raised when a database operation fails
ClassNotFoundException	This exception is raised when a class cannot be found.
InstantiationException	This exception is raised when an object cannot be instantiated.
NoSuchMethodException	This exception is raised when a method cannot be found.

What are different types of exceptions in Java?

Introduction

Types of exceptions

Exception class hierarchy in Java

Checked exceptions

List of common checked exceptions in Java

Unchecked exceptions

List of common unchecked exceptions in Java

Errors

Errors in Java

Coding example

Conclusion