Exception Hierarchy

Exceptions Hierarchy:

• Java API is providing pre-defined Exception classes and Error classes.
• Java.lang.Throwable is the super class of all exception classes.
• Exception and Error are the direct extensions (sub classes) of Throwable.
• We cannot handle Errors.
• We can handle only Exceptions.
• Exception classified into
  • Checked Exceptions
  • Unchecked Exceptions
• Child class of RuntimeException becomes unchecked exception.
• The exception class which is not child of RuntimeException is called Checked Exception.

Note: We briefly discuss about Checked and Unchecked exceptions in following concepts.

Why we cannot handle errors?

• Exception is a runtime error.
• Exception occurs while application is running.
• In case of Error, we cannot run the application.
• For example.
  • If main() is not defined, we cannot execute the code called “Error”
  • If the memory is Full, program cannot run called “Error”
  • If the class is not present that we are accessing results “Error”

class Test 
{
	// no main...
}

Compile: No error
Run: Error - no main() method