doc: Update the README.md

README.md

@@ -19,29 +19,34 @@ SELECT 1 FROM dual WHERE a = b
 
 ```text
  SQL Text
- └─Statements: net.sf.jsqlparser.statement.select.PlainSelect
- ├─selectItems -> Collection<SelectExpressionItem>
- │ └─selectItems: net.sf.jsqlparser.statement.select.SelectExpressionItem
- │ └─LongValue: 1
- ├─Table: dual
- └─where: net.sf.jsqlparser.expression.operators.relational.EqualsTo
- ├─Column: a
- └─Column: b
+ └─Statements: net.sf.jsqlparser.statement.select.Select
+ ├─selectItems -> Collection<SelectItem>
+ │ └─LongValue: 1
+ ├─Table: dual
+ └─where: net.sf.jsqlparser.expression.operators.relational.EqualsTo
+ ├─Column: a
+ └─Column: b
 ```
 
 ```java
-Statement statement = CCJSqlParserUtil.parse(sqlStr);
-if (statement instanceof PlainSelect) {
- PlainSelect plainSelect = (PlainSelect) statement;
+String sqlStr = "select 1 from dual where a=b";
 
- SelectExpressionItem selectExpressionItem =
- (SelectExpressionItem) plainSelect.getSelectItems().get(0);
+PlainSelect select = (PlainSelect) CCJSqlParserUtil.parse(sqlStr);
 
- Table table = (Table) plainSelect.getFromItem();
+SelectItem selectItem =
+ select.getSelectItems().get(0);
+Assertions.assertEquals(
+ new LongValue(1)
+ , selectItem.getExpression());
 
- EqualsTo equalsTo = (EqualsTo) plainSelect.getWhere();
- Column a = (Column) equalsTo.getLeftExpression();
- Column b = (Column) equalsTo.getRightExpression();
+Table table = (Table) select.getFromItem();
+Assertions.assertEquals("dual", table.getName());
+
+EqualsTo equalsTo = (EqualsTo) select.getWhere();
+Column a = (Column) equalsTo.getLeftExpression();
+Column b = (Column) equalsTo.getRightExpression();
+Assertions.assertEquals("a", a.getColumnName());
+Assertions.assertEquals("b", b.getColumnName());
 }
 ```