@Override
    public byte[] readChar() {
      // check the character numbers with the length
      final byte[] value = valuesReader.readBytes().getBytesUnsafe();
      return truncateIfNecesssary(value);
    }
The reader who reads from the underlying UTF8 string.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/vector/ParquetDataColumnReaderFactory.java