When do i go for static methods and when i go for non static methods ?

hi helpers,

i am having 2 years of experience in java, but still i don't know

When do i go for static methods and when i go for non static methods ?

please help me out.

Hi, I think that the methods which do not depend on and change the state of an object should be made static.

When I want a method to load at application startup .e.g. creating connection instances to db, I write it in static method. I think static method is loaded when a first reference to the class is made - some one correct if I am wrong

static methods cant work with instance variables of the class, they can only work with static variables.

so for starters, if your method is not providing instance specific behavior you could make it static.

Class - TennisPlayer
Method - getAnnualIncome() - This method needs to be an instance method as you need to create an instance first like Roger Federer and then call the getAnnualIncome() method. If you make this method static (class level), this method wouldn't know which instances (Federer's or Nadal's) income should it return, and moreover, static methods could be invoked without any instances created as well.

but if you have a method of a class not bound to any instance, go ahead and make it static
Method - static String categorizePlayer(int ranking){
if(ranking < 20){
return "champ"
}else{
return "needs practice"
}
}

So generally, utility methods are static (working only on the passed parameters), also in Singletons getInstance method is static, and methods plainly working with static variables could also be static.

I think static method is loaded when a first reference to the class is made

static blocks are executed when the class is loaded, static methods wont run until somebody invokes them.

i did not get you people explained all above.

Static methods cannot access non-static member variables or methods. So if your method needs to do that, then it cannot be static. If it doesn't, then it can be static. And if it can be static, you might as well make it static.

Another way of looking at it is - is the operation specific to that particular instance? If it uses or modified data belonging to that instance, then it can't be static.

Great explanation Matthew

. static is bounded to a class , not an Object. If a method does not take any information from a instance/field, similarly does not put any information into a instance/field of a class/object can be marked as static.

joy b chakravarty wrote: . . .
but if you have a method of a class not bound to any instance, go ahead and make it static
Method - static String categorizePlayer(int ranking){
if(ranking < 20){
return "champ"
}else{
return "needs practice"
}
} . . .

Not a good example, I am afraid; you need to know a certain player's ranking, which would be an instance field.