Volatile variable in Java is a special variable which is used to signal threads, by making a variable volatile using volatile keyword in Java, application programmer ensures that its value should always been read from main memory and thread should not used cached value of that variable from there own stack. Volatile variable also guarantees "happens-before" relationship, which means not only other thread has visibility of latest value of volatile variable but also all the variable seen by the thread which has updated value of volatile variable before this threads sees it.
