Deadlock in Threads

  • Deadlock is one of the part of multithreading.
  • synchronized keyword is used to make the class or method thread-safe which means only one thread can have lock of synchronized method and use it, other threads have to wait till the lock releases and anyone of them acquire that lock.
  • Deadlock can occur in a situation when a thread is waiting for an object lock, that is acquired by another thread and second thread is waiting for an object lock that is acquired by first thread.
  • Since, both threads are waiting for each other to release the lock, the condition is called deadlock.
Deadlock in Threads

Deadlock in Threads

Example of Deadlock in Thread

public class DeadlockExample {  
  public static void main(String[] args) {  
    final String resource1 = "MS Dhoni";  
    final String resource2 = "Virat Kholi";  
    // t1 tries to lock resource1 then resource2  
    Thread t1 = new Thread() {  
      public void run() {  
          synchronized (resource1) {  
           System.out.println("Thread 1: locked resource 1");  
  
           try { Thread.sleep(100);} catch (Exception e) {}  
  
           synchronized (resource2) {  
            System.out.println("Thread 1: locked resource 2");  
           }  
         }  
      }  
    };  
  
    // t2 tries to lock resource2 then resource1  
    Thread t2 = new Thread() {  
      public void run() {  
        synchronized (resource2) {  
          System.out.println("Thread 2: locked resource 2");  
  
          try { Thread.sleep(100);} catch (Exception e) {}  
  
          synchronized (resource1) {  
            System.out.println("Thread 2: locked resource 1");  
          }  
        }  
      }  
    };  
  
      
    t1.start();  
    t2.start();  
  }  
}

Output

Thread 1: locked resource 1
Thread 2: locked resource 2

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