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Using instanceof to check for narrower exceptions in a general catch block is often insufficient; it is usually impossible to enumerate all possible exceptions that the code could throw.

Compliant Solution (Wrapping)

Occasionally it is necessary to invoke library code that can throw any exception. While it is advisable to redesign the library code to be specific about which exceptions it throws, this is not always possible.

This compliant solution catches any exception thrown, and wraps it inside a custom exception, thereby limiting the exceptions that can be thrown.

class DoSomethingException extends Exception {
  public DoSomethingException(Throwable cause) {
    super( cause);
  }
    
  // other methods
};

private void doSomething() throws DoSomethingException {
  try {
    // code that might throw an Exception
  } catch (Throwable t) {
    throw new DoSomethingException(t);
  }
}

This code is valid by EX0 of guideline ERR14-J. Do not catch RuntimeException.

Exception wrapping is a common technique to safely handle unknown exceptions, for another example, see guideline ERR10-J. Do not let code throw undeclared checked exceptions.

Exceptions

EXC13-EX0: Classes that sanitize exceptions to comply with a security policy are permitted to translate specific exceptions into more general exceptions. This translation could potentially result in throwing RuntimeException or Exception in some cases, depending on the details of the security policy.

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