Bugfix/27 fix sonar findings on 0.3.0 (#32)

* #27: Fixed Sonar findings.

src/main/java/com/exasol/sql/ValueTableVisitor.java

@@ -0,0 +1,12 @@
+package com.exasol.sql;
+
+import com.exasol.sql.dql.ValueTable;
+import com.exasol.sql.dql.ValueTableRow;
+
+public interface ValueTableVisitor extends FragmentVisitor {
+    @Override
+    public void visit(ValueTable valueTable);
+
+    @Override
+    public void visit(ValueTableRow valueTableRow);
+}

src/main/java/com/exasol/sql/dml/rendering/InsertRenderer.java

@@ -1,7 +1,6 @@
 package com.exasol.sql.dml.rendering;
 
-import com.exasol.sql.Field;
-import com.exasol.sql.Table;
+import com.exasol.sql.*;
 import com.exasol.sql.dml.*;
 import com.exasol.sql.dql.ValueTable;
 import com.exasol.sql.dql.ValueTableRow;
@@ -12,7 +11,7 @@
  * The {@link InsertRenderer} turns SQL statement structures in to SQL strings.
  */
 // [impl->dsn~rendering.sql.insert~1]
-public class InsertRenderer extends AbstractFragmentRenderer implements InsertVisitor {
+public class InsertRenderer extends AbstractFragmentRenderer implements InsertVisitor, ValueTableVisitor {
     /**
      * Create a new {@link InsertRenderer} with custom render settings.
      *

src/main/java/com/exasol/sql/dql/SelectVisitor.java

@@ -12,8 +12,4 @@ public interface SelectVisitor extends FragmentVisitor {
     public void visit(LimitClause limitClause);
 
     public void visit(WhereClause whereClause);
-
-    public void visit(ValueTable valueTable);
-
-    public void visit(ValueTableRow valueTableRow);
 }

src/main/java/com/exasol/sql/dql/ValueTableRow.java

@@ -73,7 +73,7 @@ public static Builder builder(final Fragment root) {
      * Builder for {@link ValueTableRow}s
      */
     public static class Builder {
-        public Fragment root;
+        private final Fragment root;
         private final List<ValueExpression> expressions = new ArrayList<>();
 
         public Builder(final Fragment root) {

src/main/java/com/exasol/sql/dql/rendering/SelectRenderer.java

@@ -2,8 +2,7 @@
 
 import java.util.Optional;
 
-import com.exasol.sql.Field;
-import com.exasol.sql.Table;
+import com.exasol.sql.*;
 import com.exasol.sql.dql.*;
 import com.exasol.sql.rendering.AbstractFragmentRenderer;
 import com.exasol.sql.rendering.StringRendererConfig;
@@ -12,7 +11,7 @@
  * The {@link SelectRenderer} turns SQL statement structures in to SQL strings.
  */
 // [impl->dsn~rendering.sql.select~1]
-public class SelectRenderer extends AbstractFragmentRenderer implements SelectVisitor {
+public class SelectRenderer extends AbstractFragmentRenderer implements SelectVisitor, ValueTableVisitor {
     /**
      * Create a new {@link SelectRenderer} with custom render settings.
      *

src/main/java/com/exasol/sql/expression/BooleanTerm.java

@@ -96,8 +96,7 @@ public static BooleanExpression ge(final String left, final String right) {
      * @return instance of either {@link And}, {@link Or} or {@link Not}
      * @throws IllegalArgumentException if the operator is unknown or null
      */
-    public static BooleanExpression operation(final String operator, final BooleanExpression... expressions)
-            throws IllegalArgumentException {
+    public static BooleanExpression operation(final String operator, final BooleanExpression... expressions) {
         switch (operator.toLowerCase()) {
         case "and":
             return new And(expressions);

src/main/java/com/exasol/util/TreeNode.java

@@ -45,7 +45,7 @@ public interface TreeNode {
      * @return child node at position
      * @throws IndexOutOfBoundsException if the index is out of range (index < 0 || index ≥ size())
      */
-    public TreeNode getChild(int index) throws IndexOutOfBoundsException;
+    public TreeNode getChild(int index);
 
     /**
      * Check whether this node is the root of the tree.