layout: post

title: Statics

Static is one of the [non-access modifier](/2015/05/22/access-control.html) which has a huge role in Java. It can be used

with both variables and methods. It is used when we want some variable or method not to be a part of any specific object

of a class rather common for all objects of the class.

For example, keeping count of all the instances created for a particular class we can make the count variable `static` or

when we have a method which returns the same result irrespective of the instance invoking it like `getRandom()` returning

any random number or `getMax(int x, int y)` returning the larger number between `x` and `y` we can make the methods `static`.

As static variable/methods doesn't belong to any particular object of a class, you need not create any object to access

static variable/method. You can access directly with the help of classname and dot `'.'` operator but you can also access

normally like any other instance variable/method i.e, via object reference and dot `'.'` operator. See below:

{% highlight java linenos %}

class Frog {

static int frogCount = 0; // Declare and initialize

// static variable

int frogSize = 0;

public Frog() {

frogCount += 1; // Modify the value in the constructor

}

public static int getFrogCount() {

return frogCount;

}

public int getFrogSize() {

return frogSize;

}

public static void main(String[] args) {

Frog f = new Frog();

System.out.println(f.getFrogSize()); // Access instance

// method via object reference f

System.out.println(Frog.frogCount); // Access static

// variable via class

System.out.println(f.frogCount); // Access static

// variable via object reference f

System.out.println(Frog.getFrogCount()); // Access static

// method via class

System.out.println(f.getFrogCount()); // Access static

// method via object reference f

}

}

{% endhighlight %}

1. Static method __cannot access__ a instance(non-static) variable.

{% highlight java linenos %}

{% endhighlight %}

2. Static method __cannot access__ a instance method.

{% highlight java linenos %}

{% endhighlight %}

3. Static method __can access__ a static variable or static method.

4. Static methods __cannot be overridden__. This is an important point. Consider the below program to understand:

{% highlight java linenos %}

class Animal {

static void doStuff() {

System.out.print("a ");

}

}

class Dog extends Animal {

// it's a redefinition,

// not an override

static void doStuff() {

System.out.print("d ");

}

public static void main(String[] args) {

Animal[] a = {new Animal(), new Dog(), new Animal()};

for (int x = 0; x < a.length; x++)

a[x].doStuff();

}

}

{% endhighlight %}