Yes, this should work. However, I would recommend to use the enum class instead. If the number really has some semantic (not just an arbitrary discriminator of a constant) then this is ok, otherwise enum is better (can be used in switch, the code is more readable, etc..)
If you don't want to introduce a new file, you may want to declare the enum in the surrounding class:
public TheClass {
...
enum Item {
GOLD, ZYNC, TIN
}
...
}