Exceptions

Introduction

• Exceptions are a mechanism to detect and handle errors without writing special code to test return values.
• Error handling code for common errors can be handled in a single place.

Structure

• A try clause has to have either a catch clause or a finally clause or both.
• catch must follow try.
• finally must follow the last catch clause.

Exception Hierarchy

• All exception classes are subtypes of java.lang.Exception.
• RunTimeException is a subtype of Exception which represents unchecked exceptions. All unchecked exception will inherit from this class.
• Classes which derive from java.lang.Error indicate serious problems that an application should not try to catch. e.g OutOfMemory error.
• Both Error and Exception classes are derived from the java.lang.Throwable class.

Exception Matching

• The order of catch clauses is important. The most-specific exception type should be first, followed by the least specific.