Difference between object and class in Scala

In scala, there is no static concept. So scala creates a singleton object to provide entry point for your program execution. If you don't create singleton object, your code will compile successfully but will not produce any output. Methods declared inside Singleton Object are accessible globally. A singleton object can extend classes and traits.

Scala Singleton Object Example

object Singleton{  
    def main(args:Array[String]){  
        SingletonObject.hello()         // No need to create object.  
    }  
}  


object SingletonObject{  
    def hello(){  
        println("Hello, This is Singleton Object")  
    }  
}  

Output:

Hello, This is Singleton Object

In scala, when you have a class with same name as singleton object, it is called companion class and the singleton object is called companion object.

The companion class and its companion object both must be defined in the same source file.

Scala Companion Object Example

class ComapanionClass{  
    def hello(){  
        println("Hello, this is Companion Class.")  
    }  
}  
object CompanoinObject{  
    def main(args:Array[String]){  
        new ComapanionClass().hello()  
        println("And this is Companion Object.")  
    }  
}  

Output:

Hello, this is Companion Class.
And this is Companion Object.

In scala, a class can contain:

1. Data member

2. Member method

3. Constructor Block

4. Nested class

5. Super class information etc.

You must initialize all instance variables in the class. There is no default scope. If you don't specify access scope, it is public. There must be an object in which main method is defined. It provides starting point for your program. Here, we have created an example of class.

Scala Sample Example of Class

class Student{  
    var id:Int = 0;                         // All fields must be initialized  
    var name:String = null;  
}  
object MainObject{  
    def main(args:Array[String]){  
        var s = new Student()               // Creating an object  
        println(s.id+" "+s.name);  
    }  
} 

I am sorry, I am too late but I hope it will help you.

A class is just like any other class in other languages. You define class just like any other language with some syntax difference.

class Person(val name: String)
val me = new Person("My name")

However, object is a class with single object only. This makes it interesting as it can be used to create static members of a class using companion object. This companion object has access to private members of the class definition and it has the same name as the class you're defining.

class Person(var name: String) {

  import Person._

  def hi(): String = sayHello(name)
}

object Person {
  private def sayHello(name: String): String = "Hello " + name
}

val me = new Person("My name")
me.hi()

Also, noteworthy point is that object class is lazily created which is another important point. So, these are not instantiated unless they are needed in our code.

If you're defining connection creation for JDBC, you can create them inside object to avoid duplication just like we do in Java with singleton objects.

If you are coming from java background the concept of class in scala is kind of similar to Java, but class in scala cant contain static members.

Objects in scala are singleton type you call methods inside it using object name, in scala object is a keyword and in java object is a instance of class