Java – private constructor example

Singleton Class

The use of private constructor is to serve singleton classes. A singleton class is one which limits the number of objects creation to one. Using private constructor we can ensure that no more than one object can be created at a time. We will see in the below example how to use private constructor for limiting the number of objects for a singleton class.

package beginnersbook.com;
public class SingleTonClass {
   //Static Class Reference
   private static SingleTonClass obj=null;
   private SingleTonClass(){
      /*Private Constructor will prevent 
       * the instantiation of this class directly*/
   }
   public static SingleTonClass objectCreationMethod(){
 /*This logic will ensure that no more than
  * one object can be created at a time */
 if(obj==null){
     obj= new SingleTonClass();
 }
        return obj;
   }
   public void display(){
 System.out.println("Singleton class Example");
   }
   public static void main(String args[]){
 //Object cannot be created directly due to private constructor 
        //This way it is forced to create object via our method where
        //we have logic for only one object creation
 SingleTonClass myobject= SingleTonClass.objectCreationMethod();
 myobject.display();
   }
}

Output:

Singleton class Example