add testcase & remove unused code

src/main/java/com/alibaba/druid/sql/ast/SQLDataTypeImpl.java

@@ -57,18 +57,28 @@ public List<SQLExpr> getArguments() {
         return this.arguments;
     }
 
-    public void output(StringBuffer buf) {
-        buf.append(this.name);
-        if (this.arguments.size() > 0) {
-            buf.append("(");
-            int i = 0;
-            for (int size = this.arguments.size(); i < size; ++i) {
-                if (i != 0) {
-                    buf.append(", ");
-                }
-                ((SQLExpr) this.arguments.get(i)).output(buf);
-            }
-            buf.append(")");
-        }
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((arguments == null) ? 0 : arguments.hashCode());
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        SQLDataTypeImpl other = (SQLDataTypeImpl) obj;
+        if (arguments == null) {
+            if (other.arguments != null) return false;
+        } else if (!arguments.equals(other.arguments)) return false;
+        if (name == null) {
+            if (other.name != null) return false;
+        } else if (!name.equals(other.name)) return false;
+        return true;
     }
+
 }

src/main/java/com/alibaba/druid/sql/ast/SQLOrderBy.java

@@ -42,16 +42,24 @@ protected void accept0(SQLASTVisitor visitor) {
         visitor.endVisit(this);
     }
 
-    public void output(StringBuffer buf) {
-        buf.append("ORDER ");
-        buf.append("BY ");
-
-        int i = 0;
-        for (int size = this.items.size(); i < size; ++i) {
-            if (i != 0) {
-                buf.append(", ");
-            }
-            this.items.get(i).output(buf);
-        }
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((items == null) ? 0 : items.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        SQLOrderBy other = (SQLOrderBy) obj;
+        if (items == null) {
+            if (other.items != null) return false;
+        } else if (!items.equals(other.items)) return false;
+        return true;
     }
+
 }

src/main/java/com/alibaba/druid/sql/ast/expr/SQLBinaryOpExpr.java

@@ -24,9 +24,9 @@
 public class SQLBinaryOpExpr extends SQLExprImpl implements Serializable {
 
     private static final long serialVersionUID = 1L;
-    private SQLExpr            left;
-    private SQLExpr            right;
-    private SQLBinaryOperator  operator;
+    private SQLExpr           left;
+    private SQLExpr           right;
+    private SQLBinaryOperator operator;
 
     public SQLBinaryOpExpr(){
 
@@ -76,14 +76,6 @@ public void setOperator(SQLBinaryOperator operator) {
         this.operator = operator;
     }
 
-    public void output(StringBuffer buf) {
-        this.left.output(buf);
-        buf.append(" ");
-        buf.append(this.operator.name);
-        buf.append(" ");
-        this.right.output(buf);
-    }
-
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
             acceptChild(visitor, this.left);

src/main/java/com/alibaba/druid/sql/ast/expr/SQLCastExpr.java

@@ -50,14 +50,6 @@ public void setDataType(SQLDataType dataType) {
         this.dataType = dataType;
     }
 
-    public void output(StringBuffer buf) {
-        buf.append("CAST(");
-        this.expr.output(buf);
-        buf.append(" AS ");
-        this.dataType.output(buf);
-        buf.append(")");
-    }
-
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
             acceptChild(visitor, this.expr);

src/main/java/com/alibaba/druid/sql/ast/statement/SQLExprTableSource.java

@@ -54,4 +54,25 @@ protected void accept0(SQLASTVisitor visitor) {
     public void output(StringBuffer buf) {
         this.expr.output(buf);
     }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((expr == null) ? 0 : expr.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        SQLExprTableSource other = (SQLExprTableSource) obj;
+        if (expr == null) {
+            if (other.expr != null) return false;
+        } else if (!expr.equals(other.expr)) return false;
+        return true;
+    }
+
 }

src/main/java/com/alibaba/druid/sql/ast/statement/SQLSelectItem.java

@@ -29,15 +29,15 @@ public class SQLSelectItem extends SQLObjectImpl {
     public SQLSelectItem(){
 
     }
-    
-    public SQLSelectItem(SQLExpr expr) {
+
+    public SQLSelectItem(SQLExpr expr){
         this(expr, null);
     }
 
     public SQLSelectItem(SQLExpr expr, String alias){
         this.expr = expr;
         this.alias = alias;
-        
+
         if (expr != null) {
             expr.setParent(this);
         }
@@ -76,4 +76,29 @@ protected void accept0(SQLASTVisitor visitor) {
         }
         visitor.endVisit(this);
     }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((alias == null) ? 0 : alias.hashCode());
+        result = prime * result + ((expr == null) ? 0 : expr.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        SQLSelectItem other = (SQLSelectItem) obj;
+        if (alias == null) {
+            if (other.alias != null) return false;
+        } else if (!alias.equals(other.alias)) return false;
+        if (expr == null) {
+            if (other.expr != null) return false;
+        } else if (!expr.equals(other.expr)) return false;
+        return true;
+    }
+
 }

src/main/java/com/alibaba/druid/sql/ast/statement/SQLSelectOrderByItem.java

@@ -63,4 +63,31 @@ protected void accept0(SQLASTVisitor visitor) {
 
         visitor.endVisit(this);
     }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((collate == null) ? 0 : collate.hashCode());
+        result = prime * result + ((expr == null) ? 0 : expr.hashCode());
+        result = prime * result + ((type == null) ? 0 : type.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        SQLSelectOrderByItem other = (SQLSelectOrderByItem) obj;
+        if (collate == null) {
+            if (other.collate != null) return false;
+        } else if (!collate.equals(other.collate)) return false;
+        if (expr == null) {
+            if (other.expr != null) return false;
+        } else if (!expr.equals(other.expr)) return false;
+        if (type != other.type) return false;
+        return true;
+    }
+
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/expr/MySqlExtractExpr.java

@@ -46,13 +46,6 @@ public void setUnit(MySqlIntervalUnit unit) {
         this.unit = unit;
     }
 
-    @Override
-    public void output(StringBuffer buf) {
-        value.output(buf);
-        buf.append(' ');
-        buf.append(unit.name());
-    }
-
     protected void accept0(SQLASTVisitor visitor) {
         MySqlASTVisitor mysqlVisitor = (MySqlASTVisitor) visitor;
         mysqlVisitor.visit(this);