finish coding

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

@@ -1,10 +1,18 @@
 package dev.banking.model;
 
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
 public class BankAccount {
 
+
+
     private final int accountId;
     private long balance;
-
+    private Lock accountLock = new ReentrantLock();
+    private Condition accountCon = accountLock.newCondition();
     /*
      * Students may introduce additional fields
      * such as:
@@ -23,56 +31,78 @@ public class BankAccount {
         return accountId;
     }
 
-    /*
-     * TODO:
-     * Return the current balance in a thread-safe way.
-     *
-     * Requirements:
-     * - Must be safe under concurrent reads/writes
-     * - Should not block unnecessarily if using read/write locks
-     */
     public long getBalance() {
-        throw new UnsupportedOperationException("TODO: implement thread-safe balance read");
+        accountLock.lock();
+        try{
+            return this.balance;
+        }finally {
+            accountLock.unlock();
+        }
     }
 
-    /*
-     * TODO:
-     * Increase balance atomically.
-     *
-     * Requirements:
-     * - Must not lose updates under concurrency
-     */
+
     public void deposit(long amount) {
-        throw new UnsupportedOperationException("TODO: implement thread-safe deposit");
+        accountLock.lock();
+        try{
+            balance += amount;
+            accountCon.signalAll();
+        }finally {
+            accountLock.unlock();
+        }
     }
 
-    /*
-     * TODO:
-     * Decrease balance atomically.
-     *
-     * Requirements:
-     * - Must not cause race conditions
-     * - Negative balance handling is NOT required unless you decide
-     *   to extend the system (optional)
-     */
     public void withdraw(long amount) {
-        throw new UnsupportedOperationException("TODO: implement thread-safe withdraw");
+        accountLock.lock();
+        try{
+            while (balance < amount){
+                accountCon.await();
+            }
+            balance -= amount;
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        } finally {
+            accountLock.unlock();
         }
 
-    /*
-     * TODO:
-     * Transfer money between two accounts atomically.
-     *
-     * IMPORTANT REQUIREMENTS:
-     * - Must be atomic (no partial transfer)
-     * - Must be deadlock-free
-     * - Must protect both source and target accounts
-     *
-     * HINT:
-     * - Consider global lock ordering using accountId
-     * - Or tryLock with retry strategy
-     */
+    }
+
+
     public void transfer(BankAccount target, long amount) {
-        throw new UnsupportedOperationException("TODO: implement atomic deadlock-free transfer");
+
+        if(this.getAccountId() == target.getAccountId()){
+            return;
+        }
+
+        BankAccount first = this.getAccountId() < target.getAccountId() ? this : target;
+        BankAccount second = this.getAccountId() < target.getAccountId() ? target : this;
+
+
+        first.accountLock.lock();
+
+        try {
+
+            second.accountLock.lock();
+            try {
+
+                while (this.balance < amount) {
+                    this.accountCon.await();
+                }
+                this.balance -= amount;
+                target.balance += amount;
+
+                this.accountCon.signalAll();
+
+            }catch (InterruptedException e){
+                throw new RuntimeException();
+            }finally {
+             second.accountLock.unlock();
+            }
+
+
+
+        }finally {
+            first.accountLock.unlock();
+        }
+
     }
 }