Simple classes

Scala classes are similar to java classes but are designed to work around some of the boiler plate code. We will address multiple constructors another day. But one thing to note is that normally the code that is in a Java constructor goes directly in the body of a Scala class or in a companion object (also covered later).

1. scala> class NewClass( aPrivateInt:Int, val iAmPublic:Int, var iAmAlsoPublic:Int)
2. defined class NewClass
4. scala> val c = new NewClass(1,2,3)
5. c: NewClass = NewClass@da99836
7. scala> c.aPrivateInt
8. :7: error: value aPrivateInt is not a member of NewClass
9.        c.aPrivateInt
10.          ^
12. scala> c.iAmPublic
13. res2: Int = 2
15. scala> c.iAmAlsoPublic
16. res3: Int = 3
18. scala> c.iAmPublic = 10 // not allowed because iAmPublic is a val
19. :6: error: reassignment to val
20.        c.iAmPublic = 10
21.                    ^
23. scala> c.iAmAlsoPublic = 10 // iAmAlsoPublic is a var
25. scala> c.iAmAlsoPublic
26. res4: Int = 10
28. scala> class c2( aPrivate:Int ) {
29.      | val aPublic = aPrivate + 10
30.      | }
31. defined class c2
33. scala> class c3(tmp:Int) extends c2(tmp){
34.      | override val aPublic = tmp * 10 // can't access super.aPrivate because it
35.  is class private so use tmp
36.      | }
37. defined class c3
39. scala> new c2(10).aPublic
40. res5: Int = 20
42. scala> new c3(10).aPublic
43. res6: Int = 100
45. scala> class c4( aPrivate:Int ) {
46.      | println(aPrivate)
47.      | private val private2 = aPrivate % 10
48.      | println(private2)
49.      | }
50. defined class c4
52. scala> new c4(22)
53. 22
54. 2
55. res7: c4 = c4@64d90254