#fixed code
                              private static boolean isUnused(
      JCCompilationUnit unit,
      Set<String> usedNames,
      Multimap<String, Range<Integer>> usedInJavadoc,
      JCImport importTree,
      String simpleName) {
    String qualifier =
        ((JCFieldAccess) importTree.getQualifiedIdentifier()).getExpression().toString();
    if (qualifier.equals("java.lang")) {
      return true;
    }
    if (unit.getPackageName() != null && unit.getPackageName().toString().equals(qualifier)) {
      return true;
    }
    if (importTree.getQualifiedIdentifier() instanceof JCFieldAccess
        && ((JCFieldAccess) importTree.getQualifiedIdentifier())
            .getIdentifier()
            .contentEquals("*")) {
      return false;
    }

    if (usedNames.contains(simpleName)) {
      return false;
    }
    if (usedInJavadoc.containsKey(simpleName)) {
      return false;
    }
    return true;
  }
#vulnerable code 
                              private static boolean isUnused(
      JCCompilationUnit unit,
      Set<String> usedNames,
      Multimap<String, Range<Integer>> usedInJavadoc,
      JCImport importTree,
      String simpleName) {
    String qualifier =
        importTree.getQualifiedIdentifier() instanceof JCFieldAccess
            ? ((JCFieldAccess) importTree.getQualifiedIdentifier()).getExpression().toString()
            : null;
    if (qualifier.equals("java.lang")) {
      return true;
    }
    if (unit.getPackageName() != null && unit.getPackageName().toString().equals(qualifier)) {
      return true;
    }
    if (importTree.getQualifiedIdentifier() instanceof JCFieldAccess
        && ((JCFieldAccess) importTree.getQualifiedIdentifier())
            .getIdentifier()
            .contentEquals("*")) {
      return false;
    }

    if (usedNames.contains(simpleName)) {
      return false;
    }
    if (usedInJavadoc.containsKey(simpleName)) {
      return false;
    }
    return true;
  } 
                            #location 11 
                            #vulnerability type NULL_DEREFERENCE