ExpressionEvaluatorImpl implements ExpressionEvaluator { private Object evaluateIsNullExpression(IsNullExpression expression, DataRow dataRow) { FunctionExpression isNullExpression = new FunctionExpression(FunctionName.TYPEOF.name(), Arrays.asList(expression.getValue(), DataType.NULL)); return evaluateFunctionExpression(isNullExpression, dataRow); }  @Override Map<String, Set<String>> getColumnNames(Object expression); @Override T evaluate(Object expression, DataRow dataRow); @Override T evaluateAs(Object expression, DataRow dataRow, Class<T> cls);  }
@Test public void testEvaluateIsNullExpression() { assertThat(isNull(new Null(), EMPTY_ROW), is(true)); assertThat(isNull(2, EMPTY_ROW), is(false)); }