Implementation of checked and unchecked exceptions

Question

This is not a question what they are, but how they are implemented internally. How does compiler distinguish between checked exceptions (for example derived directly from Exception except RuntimeException) and those unchecked (for example derived from RuntimeException). Are there some special flags in exception class definitions which say what exceptions must be put in try/catch blocks or is there some specific rule in Java compiler (for example Java language design explicitly specifies the type of exceptions which are checked or not)?

Isaac · Accepted Answer · 2015-03-04 15:48:20Z

2

This is enforced by the Java compiler, and also double-checked at runtime: if a Throwable extends RuntimeException or Error, then it is deemed unchecked; all others are checked.

At runtime, this check is also enforced (remember, you can theoretically "build" Java classes at runtime).

edited Mar 4, 2015 at 15:48

answered Jan 5, 2013 at 14:19

Isaac

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Andremoniy · Accepted Answer · 2019-08-29 09:00:47Z

0

All unchecked exceptions are successors from the class RuntimeException or the class Error. All others are checked. Using reflection, for example, you can always detect which class is a superclass for this specific class of the current exception. This is the same way how Java compiler detects their types.

edited Aug 29, 2019 at 9:00

answered Jan 5, 2013 at 14:15

Andremoniy

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