### Question:
IoTDBResultMetadata implements ResultSetMetaData { @Override public String getColumnName(int column) throws SQLException { return getColumnLabel(column); } IoTDBResultMetadata(List<String> columnInfoList, String operationType,
      List<String> columnTypeList); @Override boolean isWrapperFor(Class<?> arg0); @Override T unwrap(Class<T> arg0); @Override String getCatalogName(int arg0); @Override String getColumnClassName(int arg0); @Override int getColumnCount(); @Override int getColumnDisplaySize(int arg0); @Override String getColumnLabel(int column); @Override String getColumnName(int column); @Override int getColumnType(int column); @Override String getColumnTypeName(int arg0); @Override int getPrecision(int arg0); @Override int getScale(int arg0); @Override String getSchemaName(int arg0); @Override String getTableName(int arg0); @Override boolean isAutoIncrement(int arg0); @Override boolean isCaseSensitive(int arg0); @Override boolean isCurrency(int arg0); @Override boolean isDefinitelyWritable(int arg0); @Override int isNullable(int arg0); @Override boolean isReadOnly(int arg0); @Override boolean isSearchable(int arg0); @Override boolean isSigned(int arg0); @Override boolean isWritable(int arg0);  }### Answer:
@Test public void testGetColumnName() throws SQLException { metadata = new IoTDBResultMetadata(null, null, null); boolean flag = false; try { metadata.getColumnName(1); } catch (Exception e) { flag = true; } assertEquals(flag, true); List<String> columnInfoList = new ArrayList<>(); metadata = new IoTDBResultMetadata(columnInfoList, null, null); flag = false; try { metadata.getColumnName(1); } catch (Exception e) { flag = true; } assertEquals(flag, true); String[] colums = {"root.a.b.c1", "root.a.b.c2", "root.a.b.c3"}; metadata = new IoTDBResultMetadata(Arrays.asList(colums), null, null); flag = false; try { metadata.getColumnName(colums.length + 1); } catch (Exception e) { flag = true; } assertEquals(flag, true); flag = false; try { metadata.getColumnName(0); } catch (Exception e) { flag = true; } assertEquals(flag, true); for (int i = 1; i <= colums.length; i++) { assertEquals(metadata.getColumnLabel(i), colums[i - 1]); } }