feat: add advanced multithreading banking system skeleton

src/main/java/dev/banking/model/BankAccount.java

@@ -0,0 +1,48 @@
+package dev.banking.model;
+
+public class BankAccount {
+
+    private final int accountId;
+    private long balance;
+
+    public BankAccount(int accountId, long initialBalance) {
+        this.accountId = accountId;
+        this.balance = initialBalance;
+    }
+
+    public int getAccountId() {
+        return accountId;
+    }
+
+    /*
+     * TODO
+     * Implement a thread-safe balance reader.
+     */
+    public long getBalance() {
+        throw new UnsupportedOperationException();
+    }
+
+    /*
+     * TODO
+     * Implement a thread-safe deposit operation.
+     */
+    public void deposit(int amount) {
+        throw new UnsupportedOperationException();
+    }
+
+    /*
+     * TODO
+     * Implement a thread-safe withdrawal operation.
+     */
+    public void withdraw(int amount) {
+        throw new UnsupportedOperationException();
+    }
+
+    /*
+     * TODO
+     * Implement an atomic and deadlock-free transfer.
+     */
+    public void transfer(BankAccount target, int amount) {
+        throw new UnsupportedOperationException();
+    }
+}