Errors should not be caught or handled (except in the rarest of cases). Exceptions are the bread and butter of exception handling. The Javadoc explains it well:
An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions.
Look at a few of the subclasses of Error, taking some of their JavaDoc comments:
- AnnotationFormatError - Thrown when the annotation parser attempts to read an annotation from a class file and determines that the annotation is malformed.
- AssertionError - Thrown to indicate that an assertion has failed.
- LinkageError - Subclasses of LinkageError indicate that a class has some dependency on another class; however, the latter class has incompatibly changed after the compilation of the former class.
- VirtualMachineError - Thrown to indicate that the Java Virtual Machine is broken or has run out of resources necessary for it to continue operating.
There are really three important subcategories of Throwable:
- Error - Something severe enough has gone wrong the most applications should crash rather than try to handle the problem,
- Unchecked Exception (aka RuntimeException) - Very often a programming error such as a NullPointerException or an illegal argument. Applications can sometimes handle or recover from this Throwable category -- or at least catch it at the Thread's run() method, log the complaint, and continue running.
- Checked Exception (aka Everything else) - Applications are expected to be able to catch and meaningfully do something with the rest, such as FileNotFoundException and TimeoutException...
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