Vending Machine class
I've noted a few things you could consider:


Your class should probably be VendingMachine, note the capital M.
The value 50 is a magic number and should probably be defined as a const at the top of your class.
The use of coins and tokens is confusing as they appear to refer to the same thing. Pick one term and use it everywhere.
getCans() changes the value of cans. This is a side-effect, which is generally considered a no-no, especially in a getter.
The Java idiom for decrementing is -=, so I'd change cans = cans - tokens; to cans -= tokens;
Both constructors contain similar code. I'd change the first to use the second, thus:

public Vendingmachine() {
    this(50);
}