Static Keyword

The static keyword in java is used for memory management mainly. We can apply java static keyword with variables, methods, blocks and nested class.

The static keyword belongs to the class than instance of the class.

The static can be:

1. variable (also known as class variable)

2. method (also known as class method)

3. block 4. nested class 1)

Java static variable If you declare any variable as static, it is known static variable. The static variable can be used to refer the common property of all objects (that is not unique for each object) e.g. company name of employees, college name of students etc. The static variable gets memory only once in class area at the time of class loading.

Advantage of static variable It makes your program memory efficient (i.e it saves memory). Understanding problem without static variable.

Suppose there are 500 students in my college, now all instance data members will get memory each time when object is created. All student has its unique rollno and name so instance data member is good. Here, college refers to the common property of all objects. If we make it static, this field will get memory only once.

Q) why java main method is static?

Ans) because object is not required to call static method if it were non-static method, www.testingbar.com || [e-mail] jvm create object first then call main() method that will lead the problem of extra memory allocation.

3) Java static block Is used to initialize the static data member. It is executed before main method at the time of class loading.

Can a class be static in Java? The answer is YES, we can have static class in java. But only nested classes can be static. Java allows us to define a class within another class. Such a class is called a nested class.

What are the differences between static and non-static nested classes?

1) Nested static class doesn’t need reference of Outer class, but Non-static nested class or Inner class requires Outer class reference.

2) Inner class (or non-static nested class) can access both static and non-static members of Outer class. A static class cannot access non-static members of the Outer class. It can access only static members of Outer class.

3) An instance of Inner class (or non-static nested class) cannot be created without an instance of outer class.

4) Non Static inner Class cannot contain static method.