Question

尝试编译这个，但无法弄清楚错误。几天来一直困扰着这个。是的，我是新手......任何人都可以帮助我吗？获取代码底部方法中的错误。

import java.util.ArrayList;
import java.util.Scanner;

public class BankLogic
{
    private long pNr;
    private int accountId;
    private double amount;
    private double balance;
    private double rate;

    private ArrayList<Customer> customerlist;
    private ArrayList<SavingsAccount> accounts;

    Scanner in = new Scanner(System.in);

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public BankLogic(){

        customerlist = new ArrayList<Customer>();
        accounts = new ArrayList<SavingsAccount>();
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public String toString(){

        String info = "Personnummer: " + pNr + "\nKontonummer: " + accountId
        + "\nSaldo: " + amount;
    }
    //----------------------------------------------------------------------
    // Beskrivning: returnerar presentation av alla kunder(pers.nr och namn)
    // Returvärde: String 
    //----------------------------------------------------------------------
    public String infoBank(){

        return customerlist.toString();
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public boolean addCustomer(String name, long pNr){

        for (Customer a : customerlist)
        {
            if (a.getPCode() == pNr)
                return false;
            else
            {
                Customer aCust = new Customer(name, pNr);   
                customerlist.add(aCust);
            }
        }
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public String infoCustomer(long pNr){

        for (Customer a : customerlist)
        {
            if (a.getPCode() == pNr)
            {
                System.out.println(a);
            }
        }
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public boolean changeCustomerName(String name, long pNr){

        for (Customer a : customerlist)
        {
            if (a.getPCode() == pNr)
            {
                Customer aCust = new Customer(name, pNr);   
                customerlist.add(aCust);
            }
        else
            return false;
        }
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public String removeCustomer(long pNr){

        for (int i = 0; i < customerlist.length; i++)
        {
            Customer a = customerlist.get(i);
            if (a.getPCode() == pNr)
            {
                customerlist.remove(i);
            }
            else
                i++;
        }

    }


    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public int addSavingsAccount(long pNr){

        for (Customer a : customerlist)
        {
            if (a.getPCode() == pNr)
            {
                boolean added = false;
                for (int i = 0; !added && i < accounts.size(); i++)
                {
                    added = accounts.get(i).addAccount(a);
                    if(added)
                    {
                        System.out.println("Kontonummer: " + accounts.get(i).getAccountId();
                    }
                    else 
                        return "Kontot skapades inte.";
                }
            }
        }
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public String infoAccount(long pNr, int accountId)
    {
        for (Customer a : customerlist)
        {
           if (a.getAccountId() == accountId && a.getPCode() == pNr)
               return a.infoCust();
         } 
       return null; 
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public boolean deposit(long pNr, int accountId, double amount){

        for (Customer a : customerlist)
        {
           if ((a.SavingsAccount.getAccountId() == accountId) && (a.getPCode() == pNr))
            {
                a.SavingsAccount.getBalance() = balance + amount;
            }
            else
                return false;
        }
    }

    //----------------------------------------------------------------------
    //----------------------------------------------------------------------
    public boolean withdraw(long pNr, int accountId, double amount){

        for (Customer a : customerlist)
        {
           if ((a.getAccountId() == accountId) && (a.getPCode() == pNr))
            {
                a.getBalance() = balance - amount;
                return true;
            }
            else
                return false;
        }
    }

}

Answer 1

上面的代码中有各种各样的错误，我一眼就能看到：

toString()没有返回任何内容（它只声明一个局部变量，然后在方法结束时立即进行垃圾回收）
addCustomer()并不会总是返回一些内容。
infoCustomer()和removeCustomer()永远不会返回任何内容，尽管声明它们应该在方法标题中
addSavingsAccount()应该返回一个int（根据方法标题），但只返回一个字符串 - 有时候。
除非Customer有一个名为SavingsAccount的公共字段（从很多方面来看设计很糟糕），然后a.SavingsAccount.getAccountId()和类似的错误，你可能想要Customer上的方法1}}获得其特定的储蓄账户。

您需要养成以更小的增量检查代码的习惯，至少在您掌握基本的语法方面之前。这样你就不会陷入这种情况，你需要解决大量的错误，而不知道如何修复错误。

每次添加（例如）一个方法：停止，编译，检查它是否按照您的意愿工作，然后才转到下一个方法。从长远来看，它会为你节省很多时间。

Answer 2

以下两个陈述不正确。表达式的左侧必须是变量，在您的情况下，它是一个值。

        a.SavingsAccount.getBalance() = balance + amount;


          a.getBalance() = balance - amount;

使用适当的变量或setter方法纠正它们。希望这会有所帮助。

找不到符号ArrayList

2 个答案: