Java Exception Handling Basics

Study Notes

Compile-time errors occur during compilation and indicate syntax errors or violations of Java's rules. Examples include missing semicolons, undefined variables, and type mismatches.
Runtime errors occur during program execution and are caused by unexpected situations like division by zero, accessing an out-of-bounds array element, or trying to open a non-existent file. They are also known as exceptions.
Logical errors are mistakes in program logic or algorithm that result in incorrect behavior without causing program crashes or error messages. They can be challenging to identify and require thorough debugging.

Exception Handling is a mechanism for managing unexpected events during program execution, making programs more robust.
Exceptions are events that disrupt the normal program flow, representing errors like runtime errors, I/O errors, and arithmetic errors.
Throwable class is the root of the exception hierarchy. Exceptions are represented by classes derived from this class.

Built-in Exceptions: Pre-defined exceptions available in Java libraries.
- Checked Exceptions: Checked at compile-time by the compiler. Examples include FileNotFoundException and IOException.
- Unchecked Exceptions: Not checked at compile-time. Examples include ArithmeticException, NullPointerException, and ArrayIndexOutOfBoundsException.
User-defined Exceptions: Created by extending the Exception class, allowing custom exceptions for specific scenarios.

Checked Exception:
- The provided code uses FileInputStream to read data from a file.
- The FileNotFoundException is a checked exception that needs to be handled explicitly.
Unchecked Exception:
- The code demonstrates division by zero, leading to an ArithmeticException.
- This is an unchecked exception, meaning the compiler won't force you to handle it.
User-defined Exception:
- The provided code uses the throw keyword to manually throw a user-defined exception, allowing for customized error handling.