IMoney接口：
public interface IMoney
{
public void setAmount(double a);

public double getAmount();

public String toString();
}

Money货币类：
public class Money implements IMoney
{
protected double amount=0;

public void setAmount(double a)
{
  amount=a;
}

public double getAmount()
{
  return amount;
}

public String toString()
{
  return "";
}
}

Yuan人民币类：
public class Yuan extends Money
{
public String toString()
{
  return "Y"+amount;
}
}

Dollar美元类：
public class Dollar extends Money
{
public String toString()
{
  return "$"+amount;
}
}

Action操作动作类：
public class Action
{
public void TransMoney(IMoney y,double amount)
{
  y.setAmount(amount);
  System.out.println(y);  
}

}

Application应用程序类：
public class Application
{
public static void main(String[] args)
{
  Action a=new Action();
  a.TransMoney(new Yuan(),1234);
  a.TransMoney(new Dollar(),2345);
}
}