That answer wasn't so simple at first...
But...saying the same thing in a different way:
You have two essential options...either have a public variable, or "helper" methods.
A
public variable in your 'Player' class might be,
public static int money = 0;
Then you'd change it like,
Player playerOne = new Player( ); // your instantiated object
playerOne.money += 200;
That is the un-preferred method, for people say giving direct access to variables is bad (they could tamper with them in unwanted ways)...the other would be:
A
private variable in your 'Player' class might be,
private static int money = 0;
and you have another method in this class to add money,
public static void addMoney( int amount ) {
money += amount;
}
Then to give a player money, you'd just address it with the method instead,
Player playerOne = new Player( ); // your instantiated object
playerOne.addMoney ( 200 );
And to get the money, you'd have a getter method in the Player class,
public static int getMoney( ) {
return money;
}
Both work.

...after looking at my explanation though, it's not so simple either, dang it! Anyway, hope it helps, let me know if ye' need something explained.