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javaeclipsedead-code

Eclipse gives dead code warning for reachable code (variant)

I have following code:

public String myMethod(String keyValue) {
    Map<String, Integer> keyValueToRowIndex = ...
    Integer rowIndex = (keyValue == null) ? 0 : keyValueToRowIndex.get(keyValue);
    if (rowIndex == null)
      return null;
    ...
}

Eclipse gives a "dead code" warning on the return null;. Removing the test for keyValue == null also removes the warning but I don't see how that extra test makes the return statement dead code. Clearly if the map contains no entry for some non-null keyValue, then rowIndex can still be null. Or am I missing something here?

I've seen similar Eclipse issues (here for instance), but this one seems a different and more trivial one.

Solution

  • My guess is that line 3 is interpreted as

    Integer rowIndex = Integer.valueOf((keyValue == null) ? 0 : keyValueToRowIndex.get(keyValue).intValue());

    (so both arguments to ?: are unified as int) - oddly enogh, Eclipse now shows no warning, even if it is now obvious that rowIndex is never null...

    You might also replace the 0 with Integer.valueOf(0) to make the warning disappear.