If a method is private, it means that it can not be
accessed from any class other than itself. This is the access control mechanism
provided by Java. When it is used appropriately, it can produce security and
functionality. Constructors, like regular methods, can also be declared as
private. You may wonder why we need a private constructor since it is only
accessible from its own class. When a class needs to prevent the caller from
creating objects. Private constructors are suitable. Objects can be constructed
only internally.
One application is in the singleton design pattern. The policy is that only one
object of that class is supposed to exist. So no other class than itself can
access the constructor. This ensures the single instance existence of the class.
Private constructors have been widely used in JDK, the following code is part of
Runtime class.
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public class test { private static test currenttest = new test (); public static test gettest () { return currenttest ;} // Don't let anyone else instantiate this class private test () { } }class A extends XYZ{ public static void main(String args[]) { A obj= new A(); obj.demo(); } } |