Refactor to make the code more readable and testable

src/main/java/net/sf/jsqlparser/expression/AnalyticExpression.java

@@ -26,7 +26,6 @@
 
 import java.util.List;
 import net.sf.jsqlparser.expression.operators.relational.ExpressionList;
-import net.sf.jsqlparser.statement.select.PlainSelect;
 
 /**
  * Analytic function. The name of the function is variable but the parameters following the special
@@ -38,14 +37,13 @@
  */
 public class AnalyticExpression extends ASTNodeAccessImpl implements Expression {
 
-    private ExpressionList partitionExpressionList;
-    private List<OrderByElement> orderByElements;
+    private final OrderByClause orderBy = new OrderByClause();
+    private final PartitionByClause partitionBy = new PartitionByClause();
     private String name;
     private Expression expression;
     private Expression offset;
     private Expression defaultValue;
     private boolean allColumns = false;
-    private WindowElement windowElement;
     private KeepExpression keep = null;
     private AnalyticType type = AnalyticType.OVER;
     private boolean distinct = false;
@@ -56,11 +54,11 @@ public void accept(ExpressionVisitor expressionVisitor) {
     }
 
     public List<OrderByElement> getOrderByElements() {
-        return orderByElements;
+        return orderBy.getOrderByElements();
     }
 
     public void setOrderByElements(List<OrderByElement> orderByElements) {
-        this.orderByElements = orderByElements;
+        orderBy.setOrderByElements(orderByElements);
     }
 
     public KeepExpression getKeep() {
@@ -72,11 +70,11 @@ public void setKeep(KeepExpression keep) {
     }
 
     public ExpressionList getPartitionExpressionList() {
-        return partitionExpressionList;
+        return partitionBy.getPartitionExpressionList();
     }
 
     public void setPartitionExpressionList(ExpressionList partitionExpressionList) {
-        this.partitionExpressionList = partitionExpressionList;
+        partitionBy.setPartitionExpressionList(partitionExpressionList);
     }
 
     public String getName() {
@@ -112,11 +110,11 @@ public void setDefaultValue(Expression defaultValue) {
     }
 
     public WindowElement getWindowElement() {
-        return windowElement;
+        return orderBy.getWindowElement();
     }
 
     public void setWindowElement(WindowElement windowElement) {
-        this.windowElement = windowElement;
+        orderBy.setWindowElement(windowElement);
     }
 
     public AnalyticType getType() {
@@ -168,8 +166,8 @@ public String toString() {
         }
         b.append(" (");
 
-        toStringPartitionBy(b);
-        toStringOrderByElements(b);
+        partitionBy.toStringPartitionBy(b);
+        orderBy.toStringOrderByElements(b);
 
         b.append(")");
 
@@ -184,29 +182,4 @@ public void setAllColumns(boolean allColumns) {
         this.allColumns = allColumns;
     }
 
-    private void toStringPartitionBy(StringBuilder b) {
-        if (partitionExpressionList != null && !partitionExpressionList.getExpressions().isEmpty()) {
-            b.append("PARTITION BY ");
-            b.append(PlainSelect.
-                    getStringList(partitionExpressionList.getExpressions(), true, false));
-            b.append(" ");
-        }
-    }
-
-    private void toStringOrderByElements(StringBuilder b) {
-        if (orderByElements != null && !orderByElements.isEmpty()) {
-            b.append("ORDER BY ");
-            for (int i = 0; i < orderByElements.size(); i++) {
-                if (i > 0) {
-                    b.append(", ");
-                }
-                b.append(orderByElements.get(i).toString());
-            }
-
-            if (windowElement != null) {
-                b.append(' ');
-                b.append(windowElement);
-            }
-        }
-    }
 }

src/main/java/net/sf/jsqlparser/expression/OrderByClause.java

@@ -0,0 +1,64 @@
+/*
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2018 JSQLParser
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 2.1 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Lesser Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Lesser Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ * #L%
+ */
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.statement.select.OrderByElement;
+
+import java.util.List;
+
+public class OrderByClause {
+    private List<OrderByElement> orderByElements;
+    private WindowElement windowElement;
+
+    public List<OrderByElement> getOrderByElements() {
+        return orderByElements;
+    }
+
+    public void setOrderByElements(List<OrderByElement> orderByElements) {
+        this.orderByElements = orderByElements;
+    }
+
+    public WindowElement getWindowElement() {
+        return windowElement;
+    }
+
+    public void setWindowElement(WindowElement windowElement) {
+        this.windowElement = windowElement;
+    }
+
+    void toStringOrderByElements(StringBuilder b) {
+        if (orderByElements != null && !orderByElements.isEmpty()) {
+            b.append("ORDER BY ");
+            for (int i = 0; i < orderByElements.size(); i++) {
+                if (i > 0) {
+                    b.append(", ");
+                }
+                b.append(orderByElements.get(i).toString());
+            }
+
+            if (windowElement != null) {
+                b.append(' ');
+                b.append(windowElement);
+            }
+        }
+    }
+}

src/main/java/net/sf/jsqlparser/expression/PartitionByClause.java

@@ -0,0 +1,46 @@
+/*
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2018 JSQLParser
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 2.1 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Lesser Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Lesser Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ * #L%
+ */
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.expression.operators.relational.ExpressionList;
+import net.sf.jsqlparser.statement.select.PlainSelect;
+
+public class PartitionByClause {
+    ExpressionList partitionExpressionList;
+
+    public ExpressionList getPartitionExpressionList() {
+        return partitionExpressionList;
+    }
+
+    public void setPartitionExpressionList(ExpressionList partitionExpressionList) {
+        this.partitionExpressionList = partitionExpressionList;
+    }
+
+    void toStringPartitionBy(StringBuilder b) {
+        if (partitionExpressionList != null && !partitionExpressionList.getExpressions().isEmpty()) {
+            b.append("PARTITION BY ");
+            b.append(PlainSelect.
+                    getStringList(partitionExpressionList.getExpressions(), true, false));
+            b.append(" ");
+        }
+    }
+}