When to catch java.lang.Error?

Question

In what situations should one catch java.lang.Error on an application?

Answer 1

Almost never. Errors are designed to be issues that applications generally can't do anything about. The only exception might be to handle the presentation of the error but even that might not go as planned depending on the error.

Answer 2

Ideally we should not handle/catch errors. But there may be cases where we need to do, based on requirement of framework or application. Say i have a XML Parser daemon which implements DOM Parser which consumes more Memory. If there is a requirement like Parser thread should not be died when it gets OutOfMemoryError, instead it should handle it and send a message/mail to administrator of application/framework.

Answer 3

ideally we should never catch Error in our Java application as it is an abnormal condition. The application would be in abnormal state and could result in carshing or giving some seriously wrong result.

Answer 4

An Error usually shouldn't be caught, as it indicates an abnormal condition that should never occur.

From the Java API Specification for the Error class:

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. [...]

A method is not required to declare in its throws clause any subclasses of Error that might be thrown during the execution of the method but not caught, since these errors are abnormal conditions that should never occur.

As the specification mentions, an Error is only thrown in circumstances that are Chances are, when an Error occurs, there is very little the application can do, and in some circumstances, the Java Virtual Machine itself may be in an unstable state (such as VirtualMachineError)

Although an Error is a subclass of Throwable which means that it can be caught by a try-catch clause, but it probably isn't really needed, as the application will be in an abnormal state when an Error is thrown by the JVM.

There's also a short section on this topic in Section 11.5 The Exception Hierarchy of the Java Language Specification, 2nd Edition.