usephonecard.java

关于隐藏域抽象域的例子

public class UsePhoneCard
{
  public static void main(String args[])
  {
      PhoneCard myCard=new PhoneCard(12345678,1234,50.0,"300");
      System.out.println(myCard.toString());
  }
}
class PhoneCard
{
    long cardNumber;
    private int password;
    double balance;
    String connectNumber;
    boolean connected;

    PhoneCard(long cn,int pw, double b,String s)
    {
       cardNumber=cn;
       password=pw;
       if(b>0)
           balance=b;
       else
           System.exit(1);
       connectNumber=s;
       connected=false;
    }
    boolean performConnection(long cn,int pw)
    {
       if(cn==cardNumber&&pw==password)
       {
         connected=true;
         return true;
       }
       else
       {
         connected=false;
         return false;
       }
    }
    double getBalance()
    {
      if(connected)
        return balance;
      else
        return -1;
    }
    public String toString()
    {
      String s="电话卡接入号码:"+connectNumber
           +"\n电话卡卡号:"+cardNumber
           +"\n电话卡密码:"+password
           +"\n剩余金额:"+balance;
      if(connected)
          return(s+"\n电话已接通。");
      else
          return(s+"\n电话未接通。");
     }
}