What is the difference between a static method and

Question

See the code snippets below:

Code 1

public class A {
    static int add(int i, int j) {
        return(i + j);
    }
}

public class B extends A {
    public static void main(String args[]) {
        short s = 9;
        System.out.println(add(s, 6));
    }
}

Code 2

public class A {
    int add(int i, int j) {
        return(i + j);
    }
}

public class B extends A {
    public static void main(String args[]) {
    A a = new A();
        short s = 9;
        System.out.println(a.add(s, 6));
    }
}

What is the difference between these code snippets? Both output 15 as an answer.

Answer 1

Well, more technically speaking, the difference between a static method and a virtual method is the way the are linked.

A traditional "static" method like in most non OO languages gets linked/wired "statically" to its implementation at compile time. That is, if you call method Y() in program A, and link your program A with library X that implements Y(), the address of X.Y() is hardcoded to A, and you can not change that.

In OO languages like JAVA, "virtual" methods are resolved "late", at run-time, and you need to provide an instance of a class. So in, program A, to call virtual method Y(), you need to provide an instance, B.Y() for example. At runtime, every time A calls B.Y() the implementation called will depend on the instance used, so B.Y() , C.Y() etc... could all potential provide different implementations of Y() at runtime.

Why will you ever need that? Because that way you can decouple your code from the dependencies. For example, say program A is doing "draw()". With a static language, thats it, but with OO you will do B.draw() and the actual drawing will depend on the type of object B, which, at runtime, can change to square a circle etc. That way your code can draw multiple things with no need to change, even if new types of B are provided AFTER the code was written. Nifty -

Answer 2

Another scenario for Static method.

Yes, Static method is of the class not of the object. And when you don't want anyone to initialize the object of the class or you don't want more than one object, you need to use Private constructor and so the static method.

Here, we have private constructor and using static method we are creating a object.

Ex::

public class Demo {

        private static Demo obj = null;         
        private Demo() {
        }

        public static Demo createObj() {

            if(obj == null) {
               obj = new Demo();
            }
            return obj;
        }
}

Demo obj1 = Demo.createObj();

Here, Only 1 instance will be alive at a time.

Answer 3

Static methods are useful if you have only one instance (situation, circumstance) where you're going to use the method, and you don't need multiple copies (objects). For example, if you're writing a method that logs onto one and only one web site, downloads the weather data, and then returns the values, you could write it as static because you can hard code all the necessary data within the method and you're not going to have multiple instances or copies. You can then access the method statically using one of the following:

MyClass.myMethod();
this.myMethod();
myMethod();

Non-static methods are used if you're going to use your method to create multiple copies. For example, if you want to download the weather data from Boston, Miami, and Los Angeles, and if you can do so from within your method without having to individually customize the code for each separate location, you then access the method non-statically:

MyClass boston = new MyClassConstructor(); 
boston.myMethod("bostonURL");

MyClass miami = new MyClassConstructor(); 
miami.myMethod("miamiURL");

MyClass losAngeles = new MyClassConstructor();
losAngeles.myMethod("losAngelesURL");

In the above example, Java creates three separate objects and memory locations from the same method that you can individually access with the "boston", "miami", or "losAngeles" reference. You can't access any of the above statically, because MyClass.myMethod(); is a generic reference to the method, not to the individual objects that the non-static reference created.

If you run into a situation where the way you access each location, or the way the data is returned, is sufficiently different that you can't write a "one size fits all" method without jumping through a lot of hoops, you can better accomplish your goal by writing three separate static methods, one for each location.

Answer 4

Simply put, from the point of view of the user, a static method either uses no variables at all or all of the variables it uses are local to the method or they are static fields. Defining a method as static gives a slight performance benefit.

Answer 5

- First we must know that the diff bet static and non static methods 
is differ from static and non static variables : 

- this code explain static method - non static method and what is the diff 

    public class MyClass {
        static {
            System.out.println("this is static routine ... ");

        }
          public static void foo(){
            System.out.println("this is static method ");
        }

        public void blabla(){

         System.out.println("this is non static method ");
        }

        public static void main(String[] args) {

           /* ***************************************************************************  
            * 1- in static method you can implement the method inside its class like :  *       
            * you don't have to make an object of this class to implement this method   *      
            * MyClass.foo();          // this is correct                                *     
            * MyClass.blabla();       // this is not correct because any non static     *
            * method you must make an object from the class to access it like this :    *            
            * MyClass m = new MyClass();                                                *     
            * m.blabla();                                                               *    
            * ***************************************************************************/

            // access static method without make an object 
            MyClass.foo();

            MyClass m = new MyClass();
            // access non static method via make object 
            m.blabla();
            /* 
              access static method make a warning but the code run ok 
               because you don't have to make an object from MyClass 
               you can easily call it MyClass.foo(); 
            */
            m.foo();
        }    
    }
    /* output of the code */
    /*
    this is static routine ... 
    this is static method 
    this is non static method 
    this is static method
    */

 - this code explain static method - non static Variables and what is the diff 


     public class Myclass2 {

                // you can declare static variable here : 
                // or you can write  int callCount = 0; 
                // make the same thing 
                //static int callCount = 0; = int callCount = 0;
                static int callCount = 0;    

                public void method() {
                    /********************************************************************* 
                    Can i declare a static variable inside static member function in Java?
                    - no you can't 
                    static int callCount = 0;  // error                                                   
                    ***********************************************************************/
                /* static variable */
                callCount++;
                System.out.println("Calls in method (1) : " + callCount);
                }

                public void method2() {
                int callCount2 = 0 ; 
                /* non static variable */   
                callCount2++;
                System.out.println("Calls in method (2) : " + callCount2);
                }


            public static void main(String[] args) {
             Myclass2 m = new Myclass2();
             /* method (1) calls */
             m.method(); 
             m.method();
             m.method();
             /* method (2) calls */
             m.method2();
             m.method2();
             m.method2();
            }

        }
        // output 

        // Calls in method (1) : 1
        // Calls in method (1) : 2
        // Calls in method (1) : 3
        // Calls in method (2) : 1
        // Calls in method (2) : 1
        // Calls in method (2) : 1 

Answer 6

A static method belongs to the class and a non-static method belongs to an object of a class. I am giving one example how it creates difference between outputs.

public class DifferenceBetweenStaticAndNonStatic {

  static int count = 0;
  private int count1 = 0;

  public DifferenceBetweenStaticAndNonStatic(){
    count1 = count1+1;
  }

  public int getCount1() {
    return count1;
  }

  public void setCount1(int count1) {
    this.count1 = count1;
  }

  public static int countStaticPosition() {
    count = count+1; 
    return count;
    /*
     * one can not use non static variables in static method.so if we will
     * return count1 it will give compilation error. return count1;
     */
  }
}

public class StaticNonStaticCheck {

  public static void main(String[] args){
    for(int i=0;i<4;i++) {
      DifferenceBetweenStaticAndNonStatic p =new DifferenceBetweenStaticAndNonStatic();
      System.out.println("static count position is " +DifferenceBetweenStaticAndNonStatic.count);
        System.out.println("static count position is " +p.getCount1());
        System.out.println("static count position is " +DifferenceBetweenStaticAndNonStatic.countStaticPosition());

        System.out.println("next case: ");
        System.out.println(" ");

    }
}

}

Now output will be:::

static count position is 0
static count position is 1
static count position is 1
next case: 

static count position is 1
static count position is 1
static count position is 2
next case: 

static count position is 2
static count position is 1
static count position is 3
next case: