diff --git a/w3/BankAccount.java b/w3/BankAccount.java
new file mode 100644
index 0000000..c37afb7
--- /dev/null
+++ b/w3/BankAccount.java
@@ -0,0 +1,76 @@
+package java01;
+
+public class BankAccount {
+    // 1. 私有成员变量（封装核心）
+    private String accountNumber;  // 账号（不可修改）
+    private String ownerName;      // 户主姓名（可修改）
+    private double balance;        // 余额（只能通过存取款修改）
+
+    // 2. 构造方法：创建账户时必须传入账号和户主姓名，余额初始为0
+    public BankAccount(String accountNumber, String ownerName) {
+        this.accountNumber = accountNumber;
+        this.ownerName = ownerName;
+        this.balance = 0.0;
+    }
+
+    // 3. Getter方法（对外提供查询）
+    // 账号只有getter，没有setter，保证不可修改
+    public String getAccountNumber() {
+        return accountNumber;
+    }
+
+    public String getOwnerName() {
+        return ownerName;
+    }
+
+    public double getBalance() {
+        return balance;
+    }
+
+    // 4. Setter方法：只有户主姓名可以修改
+    public void setOwnerName(String ownerName) {
+        this.ownerName = ownerName;
+    }
+
+    // 5. 存款方法 deposit
+    public void deposit(double amount) {
+        if (amount > 0) {
+            balance += amount;
+            System.out.println("存款成功！当前余额：" + balance);
+        } else {
+            System.out.println("存款失败！存款金额必须大于0。");
+        }
+    }
+
+    // 6. 取款方法 withdraw
+    public void withdraw(double amount) {
+        if (amount > 0 && amount <= balance) {
+            balance -= amount;
+            System.out.println("取款成功！当前余额：" + balance);
+        } else if (amount <= 0) {
+            System.out.println("取款失败！取款金额必须大于0。");
+        } else {
+            System.out.println("取款失败！余额不足。");
+        }
+    }
+
+    // 测试主方法（可选，用来验证功能）
+    public static void main(String[] args) {
+        // 创建一个账户
+        BankAccount account = new BankAccount("622202123456789", "张三");
+        
+        // 测试查询
+        System.out.println("账号：" + account.getAccountNumber());
+        System.out.println("户主：" + account.getOwnerName());
+        System.out.println("初始余额：" + account.getBalance());
+        
+        // 测试存款
+        account.deposit(500);
+        account.deposit(-100); // 测试错误存款
+        
+        // 测试取款
+        account.withdraw(200);
+        account.withdraw(400); // 测试余额不足
+        account.withdraw(-50); // 测试错误取款
+    }
+}
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diff --git a/w3/BankAccountTest.java b/w3/BankAccountTest.java
new file mode 100644
index 0000000..c9cf49e
--- /dev/null
+++ b/w3/BankAccountTest.java
@@ -0,0 +1,34 @@
+package java01;
+
+public class BankAccountTest {
+    public static void main(String[] args) {
+        System.out.println("========== 1. 测试账户创建 ==========");
+        BankAccount account = new BankAccount("622202123456789", "张三");
+        System.out.println("账号：" + account.getAccountNumber());
+        System.out.println("户主：" + account.getOwnerName());
+        System.out.println("初始余额：" + account.getBalance());
+        System.out.println();
+
+        System.out.println("========== 2. 测试修改户主姓名 ==========");
+        account.setOwnerName("张三丰");
+        System.out.println("修改后户主：" + account.getOwnerName());
+        System.out.println();
+
+        System.out.println("========== 3. 测试存款操作 ==========");
+        account.deposit(1000);
+        account.deposit(0);
+        account.deposit(-500);
+        System.out.println();
+
+        System.out.println("========== 4. 测试取款操作 ==========");
+        account.withdraw(300);
+        account.withdraw(800);
+        account.withdraw(0);
+        account.withdraw(-200);
+        System.out.println();
+
+        System.out.println("========== 5. 最终状态验证 ==========");
+        System.out.println("最终户主：" + account.getOwnerName());
+        System.out.println("最终余额：" + account.getBalance());
+    }
+}
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