add testcase & remove unused code

src/main/java/com/alibaba/druid/pool/DruidPooledStatement.java

@@ -18,6 +18,7 @@ package com.alibaba.druid.pool;
 import java.sql.Connection;
 import java.sql.ResultSet;
 import java.sql.SQLException;
+import java.sql.SQLFeatureNotSupportedException;
 import java.sql.SQLWarning;
 import java.sql.Statement;
 import java.util.ArrayList;
@@ -65,10 +66,6 @@ public class DruidPooledStatement extends PoolableWrapper implements Statement {
         return conn;
     }
 
-    public void setPoolableConnection(DruidPooledConnection conn) {
-        this.conn = conn;
-    }
-
     public Statement getStatement() {
         return stmt;
     }
@@ -603,11 +600,11 @@ public class DruidPooledStatement extends PoolableWrapper implements Statement {
     }
 
     public void closeOnCompletion() throws SQLException {
-
+        throw new SQLFeatureNotSupportedException();
     }
 
     public boolean isCloseOnCompletion() throws SQLException {
-        return false;
+        throw new SQLFeatureNotSupportedException();
     }
 
     @SuppressWarnings("unchecked")