Java.lang.Void Class in Java

Java.lang.Void class is a placeholder which holds a reference to a class object if it represents void keyword. It is a uninstantiable placeholder. Well, uninstantiable means that this class have a private constructor and no other constructor that we can access from outside.
Methods of lang.void class are all inherited from Object class in Java:

  • getClass() : Returns the runtime class of the argumented Object.
  • hashCode() : Returns a hash code value for the object.
  • equals() : Checks whether the two objects are equal or nor.
  • clone() : Returns a copy of the object.
  • toString() : Returns string representation of the object.
  • notify() : Wakes up a single thread that is waiting on this object’s monitor.
  • notifyAll() : Wakes up all threads that is waiting on this object’s monitor.
  • wait() : Makes current thread to wait until previous thread invokes either notify() or notifyAll() methods.
  • finalize() : Called By the garbage collector on an object when garbage collection determines that there are no more references to the object.

Reference :
Java Oracle docs

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