在java中创建类实例的麻烦

Question

public   class  PersonalAccount extends Account{
    private String cardNumber; 
    private String cardType; 

    public ArrayList<PersonalAccount> personalAccounts;
    public int personal;

   private PersonalAccount(String first, String last, String accountNumber, String cardNumber, String cardType){
        super(first, last, accountNumber);
        this.cardNumber = "";
        this.cardType = "";
    }


    public void addPersonalAccount(PersonalAccount aPersonalAccount){
        personalAccounts.add(aPersonalAccount);
    }

    public void getNumberOfPersonalAccounts(){
       personal = personalAccounts.size();

    }

    public void listAccounts(){
        for (PersonalAccount personalaccount : personalAccounts){
            System.out.println("Personal Accounts");
            System.out.println(personalaccount);
        }
    }

    public void findAccount(){
       int index = 0;
       boolean found = false;
       while(index < personalAccounts.size() && !found){
           PersonalAccount personalaccount = personalAccounts.get(index);
           if (personalaccount.getaccountNumber().equals(accountNumber)){
               found = true;
            }else{
                index++;
            }
        }
    }
}

PersonalAccount class1 = new PersonalAccount();

我试图在单击按钮时调用方法（其中numAcc是按钮）：numAcc.addactionlistener（new ActionListener（）{public void actionPerformed（ActionEvent evt）{int personal；personal=class1.getnumberofpersonalaccounts（）；}

        });

Answer 1

您没有默认的构造函数，因此不能像这样创建PersonalAccount：

PersonalAccount class1 = new PersonalAccount();

您必须传递参数first,last,accountNumber,cardNumber,cardtype。应该是这样的：

 PersonalAccount class1 = new PersonalAccount("FirstName", "Last_Name", "123456", "123456789", "Visa");

阅读以下内容：http://www.dummies.com/how-to/content/how-to-use-a-constructor-in-java.html