Java内部类如何封装逻辑？OOP内部类使用指南

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

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

    // 内部类：封装交易处理逻辑
    public class TransactionProcessor {
        public void deposit(double amount) {
            if (amount > 0) {
                balance += amount;
                System.out.println("存款: +" + amount + ", 当前余额: " + balance);
            }
        }

        public void withdraw(double amount) {
            if (amount > 0 && amount <= balance) {
                balance -= amount;
                System.out.println("取款: -" + amount + ", 当前余额: " + balance);
            } else {
                System.out.println("余额不足或金额无效");
            }
        }
    }

    // 提供获取处理器实例的方法
    public TransactionProcessor getProcessor() {
        return new TransactionProcessor();
    }
}

BankAccount account = new BankAccount("123456", 1000.0);
BankAccount.TransactionProcessor processor = account.getProcessor();
processor.deposit(500);
processor.withdraw(200);

public void startBalanceReport() {
    // 局部内部类
    class BalanceReporter implements Runnable {
        public void run() {
            System.out.println("当前余额报告: " + balance);
        }
    }
    new Thread(new BalanceReporter()).start();
}

new Thread(new Runnable() {
    public void run() {
        System.out.println("实时余额: " + balance);
    }
}).start();

public static class AccountValidator {
    public static boolean isValid(String number) {
        return number != null && number.matches("\\d{6}");
    }
}

if (BankAccount.AccountValidator.isValid("123456")) {
    System.out.println("账号格式正确");
}