Examples of errors detected by the V6021 diagnostic

V6021. The value is assigned to the 'x' variable but is not used.

Rhino

V6021 The value is assigned to the 'nameString' variable but is not used. QName.java(293)

final class QName extends IdScriptableObject {
  ....
  QName constructQName(XMLLibImpl lib,
                       Context cx,
                       Object namespace,
                       Object name) {
    String nameString = null;
    if (name instanceof QName) {
      if (namespace == Undefined.instance) {
        return (QName) name;
      } else {
        nameString = ((QName) name).localName();          // <=
      }
    }
    if (name == Undefined.instance) {
      nameString = "";
    } else {
      nameString = ScriptRuntime.toString(name);
    }
    ....
    return newQName(lib, q_uri, q_localName, q_prefix);
  }
  ....
}

Rhino

V6021 The value is assigned to the 'localMax' variable but is not used. NativeRegExp.java(568)

public class NativeRegExp extends IdScriptableObject {
  ....
  private static boolean calculateBitmapSize(....) {
    ....
    switch (src[index]) {
      case '\\':
        ....
        switch (c) {
          ....
          case 'c':
            if ((index < end) && isControlLetter(src[index]))
              localMax = (char) (src[index++] & 0x1F);         // <=
            else --index;
            localMax = '\\';
            break;
          ....
        }
      ....
    }
    // use localMax
    ....
  }
  ....
}

Huawei Cloud

V6021 Variable 'url' is not used. TriggerV2Service.java(95)

public ActionResponse deleteAllTriggersForFunction(String functionUrn)
{
  checkArgument(!Strings.isNullOrEmpty(functionUrn), ....);
  String url = ClientConstants.FGS_TRIGGERS_V2 +
               ClientConstants.URI_SEP +
               functionUrn;
  return deleteWithResponse(uri(triggersUrlFmt, functionUrn)).execute();
}

CUBA Platform

V6021 Variable 'source' is not used. DefaultHorizontalLayoutDropHandler.java(177)

@Override
protected void handleHTML5Drop(DragAndDropEvent event) {
  LayoutBoundTransferable transferable = (LayoutBoundTransferable) event
          .getTransferable();
  HorizontalLayoutTargetDetails details = (HorizontalLayoutTargetDetails) event
          .getTargetDetails();
  AbstractOrderedLayout layout = (AbstractOrderedLayout) details
          .getTarget();
  Component source = event.getTransferable().getSourceComponent(); // <=
  int idx = (details).getOverIndex();

  HorizontalDropLocation loc = (details).getDropLocation();
  if (loc == HorizontalDropLocation.CENTER
          || loc == HorizontalDropLocation.RIGHT) {
      idx++;
  }
  Component comp = resolveComponentFromHTML5Drop(event);
  if (idx >= 0) {
    layout.addComponent(comp, idx);
  } else {
    layout.addComponent(comp);
  }
  if (dropAlignment != null) {
    layout.setComponentAlignment(comp, dropAlignment);
  }
}

Similar errors can be found in some other places:

• V6021 Variable 'source' is not used. DefaultHorizontalLayoutDropHandler.java(175)
• V6021 The value is assigned to the 'r' variable but is not used. ExcelExporter.java(262)
• V6021 Variable 'over' is not used. DefaultCssLayoutDropHandler.java(49)
• And 3 additional diagnostic messages.

SpotBugs

V6021 [CWE-563] The value is assigned to the 'priority' variable but is not used. FindNonShortCircuit.java 197

private void reportBug() {
  int priority = LOW_PRIORITY;
  String pattern = "NS_NON_SHORT_CIRCUIT";

  if (sawDangerOld) {
    if (sawNullTestVeryOld) {
      priority = HIGH_PRIORITY;                                           // <=
    }
    if (sawMethodCallOld || sawNumericTestVeryOld && sawArrayDangerOld) {
      priority = HIGH_PRIORITY;                                           // <=
      pattern = "NS_DANGEROUS_NON_SHORT_CIRCUIT";
    } else {
      priority = NORMAL_PRIORITY;                                         // <=
    }
  }

  bugAccumulator.accumulateBug(
    new BugInstance(this, pattern, priority).addClassAndMethod(this), this);
}

SpotBugs

V6021 [CWE-563] The value is assigned to the 'old' variable but is not used. MergeSummarizeAndView.java 279

private void load() {
  ....
  long old = System.currentTimeMillis() - options.maxAge * (24 * 3600 * 1000L);
  if (options.baselineDate != null) {
    long old2 = options.baselineDate.getTime();
    if (old2 > old) {
      old = old2;
    }
  }
  .... // The 'old' variable is not used.
}