What makes subclass of exception checked exception

Question

Hi
When I make a exception class
class TestException extends Exception{}
This exception is a "checked exception". Understood
But the predefined java class RunTimeException is also a subclass of Exception what makes it an unchecked exception. Does compiler treat this class differently.
How I can make unchecked exception class when I extend my custom exception class from Exception.
Thanks
Abhishek

Answer 1

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But the predefined java class RunTimeException is also a subclass of Exception what makes it an unchecked exception. Does compiler treat this class differently.
How I can make unchecked exception class when I extend my custom exception class from Exception.
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The answer to both of these questions can be found in Chapter 11.2 'Compile-Time Checking of Exceptions of the Java Language Specification. Suggest you read the entire section.
http://docs.oracle.com/javase/specs/jls/se5.0/html/exceptions.html
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The unchecked exceptions classes are the class RuntimeException and its subclasses, and the class Error and its subclasses. All other exception classes are checked exception classes.
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These two other subsections give the reasons the designers of Java made the choices above
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11.2.4 Why Errors are Not Checked
11.2.5 Why Runtime Exceptions are Not Checked