interface and null safety in kotlin

Faq.txt

Q1) What is an elvis operator?
ans: It is an operator that give a default value when the original value is null.

Q2) Why do we use interface ?
ans: We use interface to achieve total abstraction.

Q3) Why can't we assign null to a normal variable?
ans: Because to eliminate the danger of null references.

Q4)What will happen if we assigned null to a normal variable?
ans:The program will give a NullPointerException.

Mcq.txt

Q1) What is the correct way to assign null ?

a) var a  = null
b) var b: String!! = null
c) var c:String?=null
d) none of the above

ans : c)

Q2) what is the output ?
  fun main()
  {
      var c: String ?= null 
      var n2=n?:"null"
      println(n2) 
  }
  
 a) not null
 b) error
 c) null
 d) nullpointerexceptio
 
 ans:c)
 
 Q3)what will be the output ?
 
       fun main() {
          var b=ddd("ko",true);
          b.get()
      }

      interface jiop{
          var b:Boolean
          fun get():Unit
      }

      class ddd(val name:String,var b:Boolean):jiop
      {
          override fun get():Unit
          {
              print("dd is ${name}")
          }
      }
      
a) null
b) error
c) dd is ko
d) none of the above

ans: error

Q4) Which is not null operator?

a) ?
b) !!
c) non null
d) none of the above

ans: b)