reentrant lock and lockInterruptibly

rahulXbarnwal · rahulXbarnwal · commit eb6861f56b52 · 2026-01-20T15:02:03.000+05:30
diff --git a/src/multithreading/locks/ReentrantExample.java b/src/multithreading/locks/ReentrantExample.java
@@ -0,0 +1,53 @@
+package multithreading.locks;
+
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class ReentrantExample {
+    private final Lock lock = new ReentrantLock();
+
+    public void outerMethod() {
+
+        // 1. lock acquired by main thread
+//        lock.lock(); // t1 ne lock le liya and innerMethod me ghus gya, and t2 wait krrha indefinitely for t1 to get finished, esko bolte hai BLOCKED/WAITING state, agar aap .lock() use krrhe to us waiting thread t2 ko interrupt nhi kr paynge
+        try {
+            lock.lockInterruptibly(); // lekin agar aapko usko interrupt krna hai, to lock ko interruptible hona bhi to chahie, to interruptexception throw hoga, to esko try/catch me krna pdega
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        try {
+            // 2.
+            System.out.println("Outer method");
+            innerMethod();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public void innerMethod() {
+        /*
+        3. jo lock phle se lock kr-rkha hai hmne usko fir se mai lock krne ka try krrha hu
+        mai apna hi wait krrha hu - deadlock
+
+        But since the lock is Reentrant
+        yani same thread holds it, to fir se whi thread acquire kr lega lock
+
+
+        Jb hm Reentrant lock use krte hai to ek count maintain hota hai, ki lock kitni baar acquire kiya gya hai
+        each lock call must be paired with an unlock call
+        lock tb release hoga jb hr ek lock match ho jayega uske unlock se
+         */
+
+        lock.lock();
+        try {
+            System.out.println("Inner method");
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public static void main(String[] args) {
+        ReentrantExample example = new ReentrantExample();
+        example.outerMethod();
+    }
+}
