idk

.idea/.gitignore

@@ -0,0 +1,10 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Ignored default folder with query files
+/queries/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
+# Editor-based HTTP Client requests
+/httpRequests/

.idea/compiler.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CompilerConfiguration">
+    <annotationProcessing>
+      <profile name="Maven default annotation processors profile" enabled="true">
+        <sourceOutputDir name="target/generated-sources/annotations" />
+        <sourceTestOutputDir name="target/generated-test-sources/test-annotations" />
+        <outputRelativeToContentRoot value="true" />
+        <module name="HW-09-Advanced-Multithreading" />
+      </profile>
+    </annotationProcessing>
+  </component>
+</project>

.idea/encodings.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="file://$PROJECT_DIR$/src/main/java" charset="UTF-8" />
+    <file url="file://$PROJECT_DIR$/src/main/resources" charset="UTF-8" />
+  </component>
+</project>

.idea/jarRepositories.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="RemoteRepositoriesConfiguration">
+    <remote-repository>
+      <option name="id" value="central" />
+      <option name="name" value="Central Repository" />
+      <option name="url" value="https://maven.devneeds.ir/" />
+    </remote-repository>
+    <remote-repository>
+      <option name="id" value="central" />
+      <option name="name" value="Maven Central repository" />
+      <option name="url" value="https://repo1.maven.org/maven2" />
+    </remote-repository>
+    <remote-repository>
+      <option name="id" value="jboss.community" />
+      <option name="name" value="JBoss Community repository" />
+      <option name="url" value="https://repository.jboss.org/nexus/content/repositories/public/" />
+    </remote-repository>
+  </component>
+</project>

.idea/misc.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="MavenProjectsManager">
+    <option name="originalFiles">
+      <list>
+        <option value="$PROJECT_DIR$/pom.xml" />
+      </list>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" project-jdk-name="25" project-jdk-type="JavaSDK" />
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

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

@@ -1,18 +1,16 @@
 package dev.banking.model;
 
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
 public class BankAccount {
 
     private final int accountId;
     private long balance;
 
-    /*
-     * Students may introduce additional fields
-     * such as:
-     * - Lock / ReentrantLock
-     * - ReadWriteLock
-     * - Object monitor
-     * - etc.
-     */
+    public final ReentrantLock lock = new ReentrantLock();
+    private final Condition sufficientFundsCondition = lock.newCondition();
 
     public BankAccount(int accountId, long initialBalance) {
         this.accountId = accountId;
@@ -23,56 +21,88 @@ 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");
+        lock.lock();
+        try {
+            return balance;
+        } finally {
+            lock.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");
+        if (amount <= 0) return;
+
+        lock.lock();
+        try {
+            balance += amount;
+            //Bonus Task
+            sufficientFundsCondition.signalAll();
+        } finally {
+            lock.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");
+        if (amount <= 0) return;
+
+        lock.lock();
+        try {
+            //Bonus Task
+            while (balance < amount) {
+                try {
+                    boolean receivedSignal = sufficientFundsCondition.await(50, TimeUnit.MILLISECONDS);
+                    if (!receivedSignal && balance < amount) {
+                        return;
+                    }
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    return;
+                }
+            }
+            balance -= amount;
+        } finally {
+            lock.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 (target == null || this == target || amount <= 0) return;
+
+        BankAccount firstAccount = this.accountId < target.getAccountId() ? this : target;
+        BankAccount secondAccount = firstAccount == this ? target : this;
+
+        firstAccount.lock.lock();
+        secondAccount.lock.lock();
+
+        try {
+            //Bonus Task
+            while (this.balance < amount) {
+                try {
+                    secondAccount.lock.unlock();
+
+                    boolean receivedSignal = this.sufficientFundsCondition.await(50, TimeUnit.MILLISECONDS);
+
+                    secondAccount.lock.lock();
+
+                    if (!receivedSignal && this.balance < amount) {
+                        return;
+                    }
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    return;
+                }
+            }
+
+            this.balance -= amount;
+            target.balance += amount;
+
+            //Bonus Task
+            target.sufficientFundsCondition.signalAll();
+
+        } finally {
+            secondAccount.lock.unlock();
+            firstAccount.lock.unlock();
+        }
     }
 }