Deprecation warning in scala

Question

I have defined a function named ti but after compilation it shows a deprecation warning. I did the same in Eclipse. The code works fine but it shows a warning.

scala>  def ti(chars:List[Char],a:List[(Char,Integer)]):List[(Char,Integer)] = {
     |    if(chars.length!=0) {
     |      var j = 1
     |      var c = chars.head
     |      for(i<-chars.tail) {
     |        if(c==i) j=j+1
     |      }
     |      a::List((c,j))
     |      ti(chars.tail,a)
     |   }
     |   else a
     | }

warning: there were 3 deprecation warnings; re-run with -deprecation for details ti: (chars: List[Char], a: List[(Char, Integer)])List[(Char, Integer)]

What is the reason for this?

Answer 1

If it tells you to re-run with -deprecation, you should do that:

k@k:~$ scala -deprecation
Welcome to Scala version 2.9.1 (OpenJDK 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.

scala> def ti(chars:List[Char],a:List[(Char,Integer)]):List[(Char,Integer)]=
     |         { if(chars.length!=0)
     |            {
     |            var j=1
     |            var c=chars.head
     |            for(i<-chars.tail)
     |            {
     |            if(c==i) j=j+1
     |            }
     |            a::List((c,j))
     |            ti(chars.tail,a)
     |            }
     |         else a
     |         }

Then you get your warnings:

<console>:7: warning: type Integer is deprecated: use java.lang.Integer instead
       def ti(chars:List[Char],a:List[(Char,Integer)]):List[(Char,Integer)]=
                                 ^
<console>:7: warning: type Integer is deprecated: use java.lang.Integer instead
       def ti(chars:List[Char],a:List[(Char,Integer)]):List[(Char,Integer)]=
                                                       ^
<console>:16: warning: type Integer is deprecated: use java.lang.Integer instead
                  a::List((c,j))
                   ^

Here the issue is that you should use java.lang.Integer or just Int if you don't need interoperability with Java. So you either import java.lang.Integer or change Integer to Int.