用java 实现一个银行账户管理系统：要求能够添加账户、删除账户、查询账户余额、存款、取款等功能。 */

好的，下面是用Java实现的银行账户管理系统。建议你将代码复制到Java IDE中并运行，以便更好地理解代码。

BankAccount类：

public class BankAccount {
    private int accountNumber;
    private String accountHolderName;
    private double balance;

    public BankAccount(int accountNumber, String accountHolderName, double balance) {
        this.accountNumber = accountNumber;
        this.accountHolderName = accountHolderName;
        this.balance = balance;
    }

    public int getAccountNumber() {
        return accountNumber;
    }

    public String getAccountHolderName() {
        return accountHolderName;
    }

    public double getBalance() {
        return balance;
    }

    public void deposit(double amount) {
        balance += amount;
    }

    public void withdraw(double amount) {
        if (balance >= amount) {
            balance -= amount;
        } else {
            System.out.println("Insufficient balance");
        }
    }

    @Override
    public String toString() {
        return "BankAccount{" +
                "accountNumber=" + accountNumber +
                ", accountHolderName='" + accountHolderName + '\'' +
                ", balance=" + balance +
                '}';
    }
}

Bank类：

import java.util.ArrayList;
import java.util.List;

public class Bank {
    private List<BankAccount> accounts;

    public Bank() {
        this.accounts = new ArrayList<>();
    }

    public void addAccount(BankAccount account) {
        accounts.add(account);
    }

    public void removeAccount(int accountNumber) {
        for (BankAccount account : accounts) {
            if (account.getAccountNumber() == accountNumber) {
                accounts.remove(account);
                return;
            }
        }
        System.out.println("Account not found");
    }

    public BankAccount getAccount(int accountNumber) {
        for (BankAccount account : accounts) {
            if (account.getAccountNumber() == accountNumber) {
                return account;
            }
        }
        System.out.println("Account not found");
        return null;
    }

    @Override
    public String toString() {
        return "Bank{" +
                "accounts=" + accounts +
                '}';
    }

    public static void main(String[] args) {
        Bank bank = new Bank();
        BankAccount account1 = new BankAccount(1001, "Tom", 1000.0);
        BankAccount account2 = new BankAccount(1002, "Jerry", 2000.0);

        bank.addAccount(account1);
        bank.addAccount(account2);
        System.out.println(bank);

        bank.removeAccount(1002);
        System.out.println(bank);

        BankAccount account3 = bank.getAccount(1001);
        if (account3 != null) {
            System.out.println("Tom's balance: " + account3.getBalance());
            account3.deposit(500.0);
            System.out.println("Tom's balance after deposit: " + account3.getBalance());
            account3.withdraw(200.0);
            System.out.println("Tom's balance after withdraw: " + account3.getBalance());
        }
    }
}

这里简单演示了如何使用这两个类。你可以根据自己的需求修改代码。