CODEWITHSUNDEEP
kotlinobject
Kiran Kittu
Kiran Kittu

Reputation: 35

What does it mean by Everything is an object in Kotlin?

What does it mean by Everything is an object in Kotlin?

In Kotlin, everything is an object in the sense that you can call member functions and properties on any variable. Some types can have a special internal representation – for example, numbers, characters and booleans can be represented as primitive values at runtime – but to the user they look like ordinary classes

Upvotes: 0

Views: 391

Answers (1)

Silvio Mayolo
Silvio Mayolo

Reputation: 70387

One of the very common criticisms of Java is that certain types, the primitive types, are treated specially. That is, there's a fundamental difference between int and String in Java. int is primitive and String is an object type. This has several downstream consequences.

  • int is always passed by value, whereas String is passed by reference.
  • int cannot be used in generics.
  • int is non-nullable, whereas String can be null.
  • You cannot call methods on int.
  • int doesn't derive from Object, so even otherwise "universal" things like toString won't work on it.

So a Java programmer always has to be conscious of this and must treat these primitive types, in some sense, differently.

Kotlin eliminates this discrepancy. In Kotlin, Int is a class type just like String. It has methods, it's passed by reference, it can be nullable (Int? is well-defined in Kotlin), and it derives from the top type Any.

Internally, Kotlin is free to optimize this to a primitive int to make your code faster. But crucially that's an implementation detail. You as the programmer are free to just assume everything is an object, and Kotlin will work with you.

Upvotes: 7

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