private String getColumnVectorType(String primitiveType) throws Exception {
    if(primitiveType.equals("double")) {
      return "DoubleColumnVector";
    } else if (primitiveType.equals("long") || isDateIntervalType(primitiveType)) {
        return "LongColumnVector";
    } else if (primitiveType.equals("decimal")) {
        return "DecimalColumnVector";
    } else if (primitiveType.equals("string")) {
      return "BytesColumnVector";
    } else if (primitiveType.equals("timestamp")) {
      return "TimestampColumnVector";
    } else if (primitiveType.equals("interval_day_time")) {
      return "IntervalDayTimeColumnVector";
    }
    throw new Exception("Unimplemented primitive column vector type: " + primitiveType);
  }
Return the argument with the first letter capitalized
vector-code-gen/src/org/apache/hadoop/hive/tools/GenVectorCode.java