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

Noncompliant Code Example

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

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

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

Compliant Solution

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

try {
  /* ... */
} catch (Exception e) {
  throw new RuntimeException(e);   // exception stack trace is propagated
}

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

Exceptions

InterruptedException, NumberFormatException, DateTimeParseException, ParseException and MalformedURLException exceptions are arguably used to indicate nonexceptional outcomes. Similarly, handling 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