Notes on Exception Hierarchy in Java

Overview

• Exceptions are structured in a hierarchy.
• Important to understand which exceptions need to be handled.

Class Hierarchy

• Object Class:
  • Every class in Java extends from the Object class by default.
• Throwable Class:
  • Two main subclasses: Exception and Error.

Key Concepts

• Exceptions:
  • Something that can and should be handled.
• Errors:
  • Issues that cannot be handled (e.g., OutOfMemoryError, I/O Error).

Exception Types

• Runtime Exception:
  • Subclass of Exception.
  • Includes common exceptions:
    • ArithmeticException
    • IndexOutOfBoundsException
    • NullPointerException
  • Unchecked Exceptions:
    • Compiler does not force handling.
• Checked Exceptions:
  • Must be handled by the programmer.
  • Example: SQL Exception, I/O Exception.

Compiler Behavior

• Unchecked Exceptions:
  • No mandatory handling by the compiler.
• Checked Exceptions:
  • Compiler requires the programmer to handle them.

Best Practices

• Handle exceptions to maintain program stability and client satisfaction.
• Even if handling a runtime exception is optional, it’s considered good practice to do so.