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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 general exception types makes code hard to understand and maintain and defeats much of the advantage of the Java exception-handling mechanism.

Noncompliant Code Example

This noncompliant code example attempts to distinguish between different exceptional behaviors by looking at the exception's message:

...

This noncompliant code example falls under ERR08-EX0 of 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.

public class TimeoutException extends Exception {
  TimeoutException () {
    super();
  }
  TimeoutException (String msg) {
    super(msg);
  }
}

// ...

try {
    doSomething();
} catch (FileNotFoundException e) {
  // Handle error
} catch (TimeoutException te) {
  // Handle error
} catch (SecurityException se) {
  // Handle error
}

Applicability

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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