Java Exception Handling

Study Notes

Compile-time Errors: Occur during compilation due to syntax violations, incorrect usage of languages, and incorrect use of reserved keywords
Runtime Errors: Occur during program execution due to unexpected situations; examples include division by zero, accessing invalid array elements, or attempting to open non-existent files.
Logical Errors: Occur when the program's logic or algorithm is incorrect and do not produce compile-time or runtime errors.

Exception: An event that occurs during the execution of a program that disrupts the normal flow of the program
Exceptions are represented by classes that are derived from the Throwable class
- Types of Exceptions:
  - Built-in Exceptions: Already defined in the Java libraries
    - Checked Exceptions: Checked by the compiler at compile time; example: FileNotFoundException
    - Unchecked Exceptions: Not checked by the compiler at compile time; example: ArithmeticException
  - User-Defined Exception: Create custom exception classes by extending the Exception class; these can be thrown using the throw keyword on specific conditions

Occur during compilation due to syntax violations or incorrect language usage.
Examples: Missing semicolons, undefined variables, incompatible types, reserved keywords used as identifiers.
Compiler generates error messages, and the program cannot be compiled until errors are fixed.

Occur during program execution due to unexpected situations or exceptional conditions.
Examples: Division by zero, accessing an array element with an invalid index, opening a non-existent file.
Result in exception objects being thrown, requiring handling using try-catch blocks.
Unhandled exceptions cause the program to terminate abruptly.

Mechanism in Java that allows handling and recovering from exceptions during program execution.
Makes programs more robust by providing a structured approach to deal with unexpected situations.

An event that disrupts the normal flow of a program during execution.
Represents various error types like runtime errors, input/output errors, and arithmetic errors.
Represented by classes derived from the Throwable class or its subclasses in Java.

Checked by the compiler during compilation.
Examples: IOException, FileNotFoundException, ClassNotFoundException
Require handling by the program using try-catch blocks or declaring them in the method signature using throws keyword.

Not checked by the compiler at compile time.
Examples: ArithmeticException, NullPointerException, ArrayIndexOutOfBoundsException
Program might not give a compilation error even if these exceptions are not handled.
Often caused by user-provided incorrect input.

Custom exceptions created by extending the Exception class.
Allow you to raise specific exceptions for unique situations in your program.
Use the throw keyword to explicitly throw these exceptions.
Require handling by the program using try-catch blocks or declaring them in the method signature using throws keyword.