Can anybody explain me what Singleton class is?

Answer 1

The Singleton's purpose is to control object creation, limiting the number of objects to one only. Since there is only one Singleton instance, any instance fields of a Singleton will occur only once per class, just like static fields. Singletons often control access to resources such as database connections or sockets.

Answer 2

A singleton pattern design returns only one instance of the class.

This could be archived by making class constructor private and creating a static method that returns only one instance.

Ex:

class Single{

private int age;
private static Single onlyOne;

private Single() {}

public static Single get(int age){

if(onlyOne == null ){
onlyOne = new Single();
}

onlyOne.age = age;

return onlyOne;

}

public void show(){
if(onlyOne != null) {
System.out.println(age) ;
}
}
}

public class Program
{
public static void main(String[] args) {
Single s = Single.get(26);
s.show();
}
}

Answer 3

similar to singleton set in maths
singleton classes have only one instance / object

Answer 4

Singleton class is the class which will instantiate only one object per JVM and it returns same object whenever required.