When handling a caught exception, the original exception's message and stack trace should be logged or passed forward.

Noncompliant Code Example

 // Noncompliant - exception is lost
try { /* ... */ } catch (Exception e) { LOGGER.info("context"); }

// Noncompliant - exception is lost (only message is preserved)
try { /* ... */ } catch (Exception e) { LOGGER.info(e.getMessage()); }

// Noncompliant - exception is lost
try { /* ... */ } catch (Exception e) { throw new RuntimeException("context"); }

Compliant Solution

try { /* ... */ } catch (Exception e) { LOGGER.info(e); }

try { /* ... */ } catch (Exception e) { throw new RuntimeException(e); }

try {
  /* ... */
} catch (RuntimeException e) {
  doSomething();
  throw e;
} catch (Exception e) {
  // Conversion into unchecked exception is also allowed
  throw new RuntimeException(e);
}

Exceptions

InterruptedException, NumberFormatException, ParseException and MalformedURLException exceptions are arguably used to indicate nonexceptional outcomes. Similarly, dealing with NoSuchMethodException is often required when dealing with the Java reflection API.

Because they are part of Java, developers have no choice but to deal with them. This rule does not verify that those particular exceptions are correctly handled.

int myInteger;
try {
  myInteger = Integer.parseInt(myString);
} catch (NumberFormatException e) {
  // It is perfectly acceptable to not handle "e" here
  myInteger = 0;
}

See