Static Variables and Methods

[Rishabh Shah]

Hello,
I have question regarding static variables and methods. we all know static variables and methods accessed by ClassName.StaticMethod
or ClassName.StaticVariable. But, I want to know that In Programs or any application, In which situation, we should make any method or variable as static. and why ?

Thanks

[Darryl Burke]

Any method or variable that is independent of the state of an instance of the class should be static.

Oh, and you might like to reply to the two responses on your previous thread.

[Fyodor Sherstobitov]

Static methods and variables belong to the class, not the instance. This means that you can access it with no need to create an object of class using ClassName.staticVariable of ClassName.staticMethod() constructions.

[Rishabh Shah]

I know that to call static method or static variables we don't need to create any object. we can call them with Class Name. but, if I develop any application or project, some situation occurs when i need to call static method or static variable i use. but, what are those situation. can you give me an example ? so, i can get better idea ....

[bhanu chowdary]

Rishabh Shah wrote:can you give me an example ? so, i can get better idea ....

A variable which maintains the number of times a page has been viewed. In this case you have to use a static variable. If you use an instance variable here you will not get the correct count.

[muralidhar nayani]

The use of static variables in real time projects are : Ticket Reservatio System in Railways or Busstations. The passenger ticket number is static it is going to increase with the perticular serial number.

In this scenario also the static variables we can use.

If the static variable value can not reinitialize.

for more visit: http://javabynataraj.blogspot.com

[Campbell Ritchie]

Welcome to the Ranch muralidhar nayani and sagar gurjar, both of you.

[John Jai]

Just to add some examples... static methods & variables are useful in counter... and in the singleton pattern..

below the id counter is static variable...

public class Student {
	private static int idCounter = 0;
	private String studentName;
	private int studentId;

	Student(String name){
		this.studentId = ++idCounter;
		this.studentName = name;
	}

	public static void main(String...args){
		Student s1 = new Student("John");
		Student s2 = new Student("Paul");

		System.out.println(s1.studentId + " .. " + s1.studentName);
		System.out.println(s2.studentId + " .. " + s2.studentName);
	}
}

below getInstance() is a static method that enables singleton pattern

class Singleton {
	private static Singleton singletonObject = new Singleton();
	
	private Singleton(){
		System.out.println("Singleton initialized only once.....");
	}
	
	public int add(int a, int b){
		return a+b;
	}
	
	public static Singleton getInstance(){
		return singletonObject;
	}	
}

public class SingletonManager {
	public static void main(String...args){
//		Singleton s1 = new Singleton(); // Gives you error when you try to create an instance for a Singleton class
		Singleton s1 = Singleton.getInstance();
		Singleton s2 = Singleton.getInstance();
		Singleton s3 = Singleton.getInstance();
		
		System.out.println(s1.add(3, 5));
		System.out.println(s2.add(4, 8));
		System.out.println(s3.add(4 ,2));
	}
}

[Rishabh Shah]

Thank you so much everyone...I got an idea now..Thanks a Lot !

[bhanu chowdary]

Rishabh Shah wrote:Thank you so much everyone...I got an idea now..Thanks a Lot !

You are welcome Rishabh

[Rishabh Shah]

its been written that
Singleton s1 = Singleton.getInstance();
Singleton s2 = Singleton.getInstance();
Singleton s3 = Singleton.getInstance();

it means that the object is created once only, but, it is reference by s1,s2,s3....is it so ?

[Rishabh Shah]

Rishabh Shah wrote:its been written that
Singleton s1 = Singleton.getInstance();
Singleton s2 = Singleton.getInstance();
Singleton s3 = Singleton.getInstance();

it means that the object is created once only, but, it is reference by s1,s2,s3....is it so ?

[bhanu chowdary]

Rishabh Shah wrote:its been written that
Singleton s1 = Singleton.getInstance();
Singleton s2 = Singleton.getInstance();
Singleton s3 = Singleton.getInstance();
it means that the object is created once only, but, it is reference by s1,s2,s3....is it so ?

Yes. For more information please read Singleton Pattern

[Campbell Ritchie]

Agree, but beware: many people nowadays think singletons are not a good design pattern; indeed some people say "singleton antipattern".

[bhanu chowdary]

Campbell Ritchie wrote:Agree, but beware: many people nowadays think singletons are not a good design pattern; indeed some people say "singleton antipattern".

Campbell, Could you please explain this in detail?

[Campbell Ritchie]

No. But try here, and search the Ranch for similar posts.