update:demo9

com/study/demo9/Outer.java

@@ -0,0 +1,30 @@
+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;
+        }
+    }
+}