Singleton Class in java

Singleton Design Pattern :-
it Limits no of object creation of that class is only one. Only one instance of the class we can create in the whole application.

1. Make a public class.
2. Declare variable of private and static type that will object of the class.
3. Create a private constructor .
4. Make a public static method which well return instance of the class.

Example are follows:-

public class SingletonClass {

  private static SingletonClass singletonClass = null;

  private SingletonClass() {
  }

  public static synchronized SingletonClass getInstance() {
    if (singletonClass == null) {
      singletonClass = new SingletonClass();
    }
    return singletonClass;
  }
}

Example: To test that object is created only one below we can test

SingletonClass a=SingletonClass.getInstance();
SingletonClass b=SingletonClass.getInstance();
SingletonClass c=SingletonClass.getInstance();

System.out.println(a.hashCode());
System.out.println(b.hashCode());
System.out.println(c.hashCode());
Output:-
1791741888
1791741888
1791741888