Static Members :

• Class members prefix with non-access modifier static, are called static members.

• Static members are not particular to objects.

• Most often, these represent public resource (data) like DB connection or services (methods) common to all object of the class.

• They are accessed with just class name.

Example:

class Math
{
  public static final float PI = 3.14F;
}
To access PI, we don not need to instantiate Math. We will just use the following :-
System.out.println(Math.PI);

• Static data fields (either variable or constants)
• Static methods
• Static block
• Static nested class

Static Variable :

• A variable marked as static is known as static variable.

• It is also refer as class variable.

• Static variable gets memory only once in class area at the time of class loading, and destroys when the program stops.

• There would only be one copy of each class variable(static variable) per class, regardless of how many objects are created from it.

• It is useful when we want to share a common property to all objects.

Example :

class Demo
{
 int x;
 static int y;
public static void main(String []arg)
 {
  Demo ob1 = new Demo();
  Demo ob2 = new Demo();
 }
}

 Here y is static variable of integer type in class Demo.
 There will be a single copy of y created for all instance of Demo class.

class Demo
{
 int x;
 static int y;
 void counter()
 {
   x++;
   y++;
  System.out.println("x :"+x);
  System.out.println("y :"+y);
 }
 public static void main(String []arg)
 {
  Demo ob1 = new Demo();
  ob1.counter();
  Demo ob2 = new Demo();
  ob2.counter();
 }
}           

x :1
y :1
x :1
y :2        

Static Methods :

• A method declared with static modifier is called static method.

• A static method can access other static members (data or methods) in the same class directly.

• A static method can’t access non-static members of the class directly. An object is required.

• In a static method, we can’t use this or super.

• To call a static method object is not required.

Example

class Demo
{
 int x;
 static int y;
 static void show()
 {
  System.out.println("static method");
  // y is direct accessed
  System.out.println("y :"+y);
 }
 public static void main(String []arg)
 {
  //Object is not required
   Demo.show();
//Direct access in static method in same class
   show();
  // may access with object as well
   Demo ob = new Demo();
   ob.show();// not recommonded
   //for x object is required
  System.out.println("x :"+ob.x);
 }
}