how to remove MongoInternalException?

I am trying to perform CRUd operations in mongodb and scala.. i have written following code.this code is compiling succesfully but giving runtime exception.I am using scala 2.8.can any 1 help me out?

Error while execution:

Exception in thread "main" com.mongodb.MongoInternalException: DBPort.findOne failed at com.mongodb.DBPort.findOne(DBPort.java:153) at com.mongodb.DBPort.runCommand(DBPort.java:159) at com.mongodb.DBTCPConnector.testMaster(DBTCPConnector.java:369) at com.mongodb.Mongo.(Mongo.java:140) at com.mongodb.Mongo.(Mongo.java:124) at com.mongodb.Mongo.(Mongo.java:81) at QuickTour.main(QuickTour.java:16) Caused by: java.io.IOException: couldn't connect to [/127.0.0.1:8005] bc:java.net.ConnectException: Connection refused: connect at com.mongodb.DBPort._open(DBPort.java:205) at com.mongodb.DBPort.go(DBPort.java:85) at com.mongodb.DBPort.findOne(DBPort.java:145) ... 6 more

// crud.scala

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;

object crud
{
  def main(args:Array[String])
  {
    while(true)
    {
      println("")
      println("1.Insert ")
      println("2. Retriever ")
      println("3. Update")
      println("4. Delete")
      println("5. Exit")
      println("")
      println("Enter choice : ")

      val ch=Console.readInt

      ch match
      {
        case 1=>
          insert();
        case 2=>
          retrieve() ;
        case 3=>
          update();
        case 4=>
          delete();
        case 5=>
          System.exit(0)
      }
    }
  } //main

  def insert()
  {
    println("Enter the rollno")
    var roll=Console.readInt

    println("Enter the name")
    var name=Console.readLine

    println("Enter the age")
    var age=Console.readInt

    println("Enter the city")
    var city=Console.readLine

    println("Enter the marks")
    var marks=Console.readInt

    val mongo = new Mongo();

    var databaseName = mongo.getDB("mydb")
    var collectionName = databaseName.getCollection("student")
    val dbObject = new BasicDBObject()
    dbObject.put("rollno", "roll")
    dbObject.put("name", "name")
    dbObject.put("age", "age")        
    dbObject.put("city", "city")        
    collectionName.insert(dbObject);
    println("Inserted succesfully");
  }

  def retrieve()
  {
    println("Enter the rollno")
    var r=Console.readInt
    val mongo = new Mongo()

  开发者_JS百科  var databaseName = mongo.getDB("mydb")
    var collectionName = databaseName.getCollection("student")

    val query=new BasicDBObject();
    val query1=new BasicDBObject();
    query.put("marks",new BasicDBObject("$gt","70"));
    var cursor = new DBCursor(collectionName,query,query1)
    println("The list of students is")
    while(cursor.hasNext)
    {
      println(cursor.next());
    }
  } //retrieve

  def update()
  {
    println("Enter the rollno of student to be updated")
    var no=Console.readInt

    val mongo = new Mongo()

    var databaseName = mongo.getDB("mydb")
    var collectionName = databaseName.getCollection("student")
    val query=new BasicDBObject();
    val query1=new BasicDBObject();
    query.put("rollno",new BasicDBObject("$eq",no));
    var cursor = new DBCursor(collectionName,query,query1)
  }

  def delete()
  {
    println("Enter the rollno of student to be deleted")
    var no=Console.readInt

    val mongo = new Mongo()
    var databaseName = mongo.getDB("mydb")
    var collectionName = databaseName.getCollection("student")
    val query=new BasicDBObject();
    val query1=new BasicDBObject();
    query.put("rollno",new BasicDBObject("$eq",no));
    var cursor = new DBCursor(collectionName,query,query1)

    while(cursor.hasNext)
    {
      collectionName.remove(cursor.next())
    }
  } //delete
}

The error says "couldn't connect to [/127.0.0.1:8005]" you could start with making sure that MongoDB is running, and that it's running on that port. The standard MongoDB port is 27017.