Java：构造函数和参数列表错误

Question

public class Agora extends CreditCardPayment {

public void run() {

CashPayment ad1 = new CashPayment(12f);
ad1.paymentDetails();

CashPayment ad2 = new CashPayment(156.4f);
ad2.paymentDetails();

int cardnum1 = 1253462136;
CreditCardPayment ad3 = new CreditCardPayment(325.99f , "Visa" , "12/1/2015" , cardnum1);
ad3.paymentDetails();

int cardnum2 = 1235623151;
CreditCardPayment ad4 = new CreditCardPayment(999.99f , "Master" , "25/6/2016" , cardnum2);
ad4.paymentDetails();
 }
}

public class CreditCardPayment extends Payment{

public CreditCardPayment(float x ,String name , String exp_date , int card_num) {
 super (x);
 Card_name = name;
 Expiration_date = exp_date;
 Card_number = card_num;
 }

public String paymentDetails() {
  return super.paymentDetails() + "Card's name :" + Card_name + " , Expiration Date :" + Expiration_date + " , Card Number :" + Card_number ;
  }

  private String Card_name;
  private String Expiration_date;
  private int Card_number;
  }

Answer 1

基于@clcto的评论：Java为类提供了一个无参数的默认构造函数，除非您指定了一个或多个其他构造函数。您已经为CreditCardPayment提供了构造函数，因此该类没有no-arg构造函数。

您没有为Agora提供构造函数，因此默认行为是假设一个no-arg构造函数，就像您已经编写了

public Agora() {
    super();
}

但是超类(CreditCardPayment)没有no-arg构造函数，所以这是失败的。