Value get is not a member of java.io.Serializable - scala

Question

I have written 2 codes .The functionality of both the code is same.Both the codes take user data then store it in map and on providing keys we get correspoding user data. I have written an extra logic in code2, whic I have mentioned below.
Code1:
class user(var name:String,var id:Int, var gender:Option[String])
{
override def toString="("+ name+","+id+","+gender+")"
}
object a
{
def main(args:Array[String]):Unit={
var a=new user("kl",90,Some("Male"))
println(a.name,a.id,a.gender)//ACESS VALUES
//DEFINING MAP
var mm=Map(1-> new user("jh",189,Some("Male")),2->new user("gh",12,None),3
->new user("io",100,Some("Female")))
// defining method giving o/p value of specific key of mm
def getkey(i:Int)=
{ mm.get(i)
}
var u1=getkey(readLine("ENTER THE KEY").toInt) // some[user]
println(u1.getClass.getName)
if(u1.isDefined)
{
println(u1.get+","+u1.get.name+","+u1.get.id+","+u1.get.gender)
}
}
}
Code1 1 works properly and O/P is right. I have added extra logic in Code2. The extra logic is getKey method. I have written a code for checking whether the input key is present in map. There I am getting an error:
**value get is not a member of java.io.Serializable**_
Code2:
class user(var name:String,var id:Int, var gender:Option[String])
{
override def toString="("+ name+","+id+","+gender+")"
}
object a
{
def main(args:Array[String]):Unit={
var a=new user("kl",90,Some("Male"))
println(a.name,a.id,a.gender)//ACESS VALUES
//DEFINING MAP
var mm=Map(1-> new user("jh",189,Some("Male")),2->new user("gh",12,None),3-> new user("io",100,Some("Female")))
// defining method giving o/p value of specific key of mm
def getkey(i:Int)=
{
//EXTRA LOGIC
var a=(mm.keys).toList
if(a.contains(i)){mm.get(i)}
else {"NO SUCH ELEMENT EXCEPTION , KEY DOESNT MATCH"}
}
print("ENTER THE KEY \n")
var u1=getkey(1) // some[user]
println(u1.get)
}
}
ERROR -
enter code here
eg1.Option.scala:27: error: value get is not a member of
java.io.Serializable
println(u1.get)
^
one error found
Why does the seriliazable errors occurs in Code2 and not in Code1? Is the error due extra logic in Code2? How to fix an error?
Thank you!

Answer 1

It happens because your getKey function return type is io.Serializable.
Reason for this is that every branch of your if expression is returning a different type:
def getkey(i:Int) = { // io.Serializable
//EXTRA LOGIC
var a=(mm.keys).toList
if(a.contains(i)) { mm.get(i) } // option here
else { "NO SUCH ELEMENT EXCEPTION , KEY DOESNT MATCH" } // string here
}
Consider rewriting your function, so its return type is Option[User], one way of doing so is:
def getkey(i:Int): Option[user] = {
//EXTRA LOGIC
var a=(mm.keys).toList
if(a.contains(i)) { mm.get(i) }
else { None }
}
However, there is no need for checking keys, you can simplify this function to:
def getkey(i:Int): Option[user] = {
//EXTRA LOGIC
m.get(i)
}
Hint: write expected return type for functions to see what's going wrong in such cases.