Java/com/study/demo9/Outer.java

package com.study.demo9;

public class Outer {
    public static void main(String[] args) {
        Account account = new Account("张三", 1000.0);
        System.out.println("Can pay 500: " + account.canPay(500));
        System.out.println("Can pay 1500: " + account.canPay(1500));
    }
}

class Account {
    private String ownerName;
    private double balance;

    public Account(String ownerName, double balance) {
        this.ownerName = ownerName;
        this.balance = balance;
    }

    public boolean canPay(double amount) {
        SecurityChecker checker = new SecurityChecker();
        return checker.checkBalance(amount);
    }

    class SecurityChecker {
        boolean checkBalance(double amount) {
            return balance >= amount;
        }
    }
}