java - 将 Account 对象添加到 ArrayList

Question

public class Bank {
    private ArrayList<Account> accounts;
    private int numberOfAccounts;

    public Bank() {
        numberOfAccounts = 0;
        accounts = new ArrayList<Account>();
    }

    public int getNumOfAccounts() {
        return numberOfAccounts;
    }

    public void addAccount(Account a) {
        numberOfAccounts++;
        accounts.add(a);
    }

    public Account findAccount(int id) {
        int index = id - 1;
        if (accounts.size() >= id){
            return accounts.get(index);
        }
        else return null;
    }

    public void addMonthlyInterest() {
        for (Account x : accounts) {
            x.addMonthlyInterest();
        }
    }

    public void removeAccount(Account a) {
        numberOfAccounts--;
        accounts.remove(a);
    }
}

因此，当我将帐户添加到 ArrayList，然后检查大小时，它一直告诉我其中没有任何内容。我使用 .add() 添加的方式有问题吗？

这是我的 BankTest 的一部分。我不太确定 testAddAccount 使用什么(JUnit 方面)，但我知道它们没有被添加，因为当我尝试查找帐户时，它们都不存在。

import static org.junit.Assert.*;
import static org.junit.Assert.assertEquals;

import java.util.ArrayList;

import org.junit.Test;

public class BankTest {
    private final ArrayList<Account> accounts = new ArrayList<Account>();
    private Bank bank = new Bank();
    private java.util.Random rand;
    // private static final double[] RATES;
    // private static final int[] TYPES;

    SavingsAccount sa = new SavingsAccount(0.034);
    CheckingAccount ca = new CheckingAccount(0.034, 100);
    CreditCardAccount cca = new CreditCardAccount(0.034, 100);

    @Test
    public void testAddAccount() {
        // Tests Bank.addAccount() by adding many random accounts to the bank.
        // SavingsAccount sa = new SavingsAccount(0.034);
        SavingsAccount sa = new SavingsAccount(0.034);
        CheckingAccount ca = new CheckingAccount(0.034, 100);
        CreditCardAccount cca = new CreditCardAccount(0.034, 100);
        bank.addAccount(sa);
        bank.addAccount(ca);
        bank.addAccount(cca);
        if (accounts.size() == 3){
            System.out.println("true");
        }else System.out.println("false");

    }

    @Test
    public void testFindAccount() {
        // Tests Bank.findAccount() by finding all existing accounts and
        // attempting to find some non-existing accounts.
        bank.addAccount(sa);
        bank.addAccount(ca);
        bank.addAccount(cca);

        int size = accounts.size();
        System.out.println(size);
        accounts.get(0);
        assertEquals(sa, bank.findAccount(1));
        assertEquals(ca, bank.findAccount(2));
        assertEquals(cca, bank.findAccount(3));

        assertNull(bank.findAccount(50));
        assertNull(bank.findAccount(80));
        assertNull(bank.findAccount(230));

    }

}

Answer 1

我需要看看你如何实例化和使用 Bank 对象，但我猜这就是你的问题所在。每当您创建新银行时，帐户列表都会初始化 - 每当您尝试访问帐户列表时，您是否都会创建新银行？