public class Card{
    int id;
    int balance;
    Card(int id,int balance){
        this.id=id;
        this.balance=balance;
    }
    void withdraw(int amount){
        balance-=amount;
    }
    void deposit(int amount){
        balance+=amount;
    }
    void print(){
        System.out.printf("Card id:%10d \nBalance:$%8.2d",id,balance);
    }
}
class CardTest{
    public static void main(String args[]){
        Card a=new Card(1,500);
        Card b=open(2);
        transfer(a,b,120);
        a.print();
        b.print();
    }
    static Card open(int id){
        return new Card(id,0);
    }
    static void transfer(Card from,Card to,int amount){
        from.withdraw(amount);
        to.deposit(amount);
        Card temp=from;
        from=to;
        to=temp;
    }
}

[ 本帖最后由 long8855381 于 2014-4-12 18:42 编辑 ]