What Is a Private Java Constructor and Why Is It Useful?

java constructor

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During your IT interview, you may be asked to describe a private Java constructor and to name its main uses. Let us tell you the most important details you need to know about this so that you can ace your interview. Take a look!

What Is a Private Java Constructor?

A private constructor can make sure that no more than a preset number of objects (usually one object) is created as by a class. It can do so by preventing the class from being instantiated by the caller. The main use of private Java constructors is to serve singleton classes. These are classes that limit the number of objects that are created to one.

Types of Classes Where a Private Java Constructor Is Useful

Private constructors are particularly useful for the following types of classes:

  • Classes which only include static utility methods
  • Type-Safe Enumerations
  • Singleton Classes
  • Classes which only include constants

Private Java Constructors in Singleton Design Patterns

When private constructors are used for singleton classes, the main result is that it will only relay one object. Moreover, the creation of multiple objects is strictly forbidden. The caller will not be able to create more than one object.

Private Java Constructors in Type-Safe Enumerations

When private constructors are used in type-safe enumeration classes, the number of objects created by the class can be limited. In this case, the class will be able to relay more than one object, but no more than the limit impose by the private constructor. This means that callers will be able to create more than one object, but they will be obligated to remain within the imposed limit.

Private Java Constructors in Static Utility Method Classes

In the case of static utility method classes, private constructors can be used to forbid object construction entirely. Neither the caller or the native class will be able to construct objects by instantiating that class. It important that you know that private Java constructors are also able to prevent the creation of objects entirely.

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