Can Constructors be Private ?

Yes, a constructor can be private. A private constructor can be useful in many ways.

It prevents instantiation outside the object. If we make the constructor private then it can only be accessed inside that class. For example, in the following software design patterns we can use it:

- Singleton Patter
- Factory Pattern

It prevents sub-classing. If we make an private constructor, no other classes can extend that class. It's kind of using the final keyword.

Lets, look at the code of a Singleton Pattern:

Comments

Difference between abstract class and interface in OOP

Source: Amit Sethi In Interface: > All variables must be public static final. > No constructors. An interface can not be instantiated using the new operator. > All methods must be public abstract .

DFS Performance Measurement

Completeness DFS is not complete, to convince yourself consider that our search start expanding the left subtree of the root for so long path (maybe infinite) when different choice near the root could lead to a solution, now suppose that the left subtree of the root has no solution, and it is unbounded, then the search will continue going deep infinitely, in this case , we say that DFS is not complete. Optimality Consider the scenario that there is more than one goal node, and our search decided to first expand the left subtree of the root where there is a solution at a very deep level of this left subtree , in the same time the right subtree of the root has a solution near the root, here comes the non-optimality of DFS that it is not guaranteed that the first goal to find is the optimal one, so we conclude that DFS is not optimal. Time Complexity Consider a state space that is identical to that of BFS, with branching factor b, and we start the search from th

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