update:demo2

com/study/demo2/Account.java

@@ -0,0 +1,36 @@
+package com.study.demo2;
+
+public class Account {
+    private String accountId;
+    private String owner;
+    private double balance;
+
+    public Account(String accountId, String owner, double balance) {
+        this.accountId = accountId;
+        this.owner = owner;
+        this.balance = balance;
+    }
+
+    public void deposit(double amount) {
+        if (amount > 0) {
+            balance += amount;
+        }
+    }
+
+    public void withdraw(double amount) {
+        if (amount > 0 && amount <= balance) {
+            balance -= amount;
+        }
+    }
+
+    public void transfer(Account target, double amount) {
+        if (amount > 0 && amount <= balance) {
+            this.balance -= amount;
+            target.balance += amount;
+        }
+    }
+
+    public double getBalance() {
+        return balance;
+    }
+}