Difference between revisions of "Exceptions"
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== Exception Matching == | == Exception Matching == | ||
| − | * The order of catch clauses is important. The most-specific exception type should be first, followed by the more general exceptions. Otherwise, the code will not compile. | + | * The order of catch clauses is important. |
| − | * | + | * If the exceptions are in the same class hierarchy, The most-specific exception type should be first, followed by the more general exceptions. Otherwise, the code will not compile. |
| + | * If exceptions are in different class hierarchy, then the order does not matter. | ||
[[Category:OCPJP]] | [[Category:OCPJP]] | ||
Revision as of 00:56, 20 July 2011
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.
- If the exceptions are in the same class hierarchy, The most-specific exception type should be first, followed by the more general exceptions. Otherwise, the code will not compile.
- If exceptions are in different class hierarchy, then the order does not matter.
