programmers_k_aada

java.util.concurrent.lock package{1.5 version} Problem with tradition synchronized  keyword: We are not having any flexibility to try for a lock without waiting. There is no way to specify the maximum waiting   time for a thread to get the lock whereas in tradition synchronized thread will wait until getting the lock which may cause performance problems or deadlock. In  tradition synchronized,  if a thread releases the lock then which waiting thread will get that lock we are not having control over this To overcome this problem sun organization introduces java.util.lock package in JDK 1.5v. It also provides several enhancement to the programmers.  Lock Interface: Lock object is similar to the implicit lock to execute synchronized methods or blocks. Lock interface provides more extensive operation than traditional lock(synchronized). Important methods of Lock interface: void lock() - we can use this method to acquire a lock.       Different Cases:...

ThreadGroup: Based on the  functionality we can group thread into a single unit which is nothing but a thread group i.e a thread group contains a group of threads. In addition to that, it also contains a sub-thread group The main advantage of maintaining threads in the form of the thread group is we can perform common operations very easily. Note:-1. Every thread in java belong to some group, main thread belong to the main group            2. Every thread group in java is the child group of the system group either directly or indirectly, hence a system group act as root/parent for all thread groups. System group contains several system levels thread:  1. finalizer  2. Reference handler  3. Attach Listener  4. Signal Dispatcher, etc. Program to illustrate that every thread in java belongs to some group and directly or indirectly child of system group:  import java.lang.*; class ThreadGroupDemo1{    public static void m...

Daemon Thread:   1 . The thread which are executing in background is called Daemon thread .         For example:-Garbage Collector,Signal Dispatcher,Attach Listener etc.       2.The main objective of daemon Thread is to provide support to Non-daemon thread .       3. Usually daemon thread having low priority but based on our requirement daemon thread can also run with high priority by JVM .      4. By default main thread is always non-daemon and for all remaining thread daemon nature is inherited i.e if the parent thread is daemon then automatically child thread is also daemon and vice -versa.  5.JVM terminate all daemon thread when all user thread finish their execution.     Note:-Changing nature of thread to daemon is only possible before starting a thread .After starting a thread if we are trying to change thread to daemon thread then it will throw an exception illegalThreadStateException on run...

Program On DeadLock:     import java.util.*;     class A{        public synchronized void d1(B b)          {             System.out.println("Thread start executing d1() method");             try{               Thread.sleep(5000);               }catch(Exception e){}            System.out.println("Thread try to invoke B's last()");             b.last();        }      public synchronized void last()      {          System.out.println("last() method of A's class");      }    }     class B{        public synchronized void d2(A a)          {             System....

What is DeadLock? if two thread executing on two different objects.  Let's assume thread t1,t2 and objects ob1 ,ob2   t1 got the lock of object ob1.   t2 got the lock of object ob2. let's assume the situation when t1 wann a execute method which is present in ob2(t2 has a lock on ob2) and  t2 wanna execute method which is present in ob1(t1 has a lock on ob1).  Note-Both methods are synchronized.     Thread t1 asked t2 to release the lock of object ob2. So that t1 can execute the method present in ob2. But t2 disagree to release the lock of object ob2 and t2 asked t1 the same thing what t1 has asked for t2 to do.t1 also disagrees with t2. Both threads not to release lock is simple stubbornness(zidd in Hindi). This is the only reason for infinite waiting which is called deadlock. Points about DeadLock: If two thread is waiting for each other forever. Such type of infinite waiting is called DeadLock. Synchronized Keyword is the only reason for the DeadLock...