Because an exception is caught by its type, it is better to define exceptions for specific purposes than to use the general exception types for multiple purposes. Throwing the general exception types makes code hard to understand and maintain , and defeats much of the advantage of the Java exception-handling mechanism.
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If doSomething() throws an exception or error whose type is a subclass of Throwable, the switch statement allows selection of a specific case to execute. For example, if the exception message is "file not found," the appropriate action is taken in the exception-handling code.
However, any change to the exception message literals involved will break the code. For example, suppose this code gets is executed:
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throw new Exception("cannot find file");
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This exception should be handled by the first case clause, but it will be rethrown because the string does not match any case clause.
Furthermore, exceptions may be thrown without a message.
This noncompliant code example falls under ERR08-EX0 of rule ERR08-J. Do not catch NullPointerException or any of its ancestors because it catches general exceptions but rethrows them.
Compliant Solution
This compliant solution uses specific exception types and defines new special-purpose exception types where required.
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Exceptions are used to handle exceptional conditions. If an exception is not caught, the program will be terminated. An exception that is incorrectly caught or is caught at the wrong level of recovery will often cause incorrect behavior.
Bibliography
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