static: used for properties or functions of class or struct and can be accessed by class/struct level. With static keyword, we cannot override. final: used for class and class members (properties or functions). With final keyword, we cannot override.
The only difference between final and const is that the const makes the variable constant from compile-time only. Using const on an object, makes the object's entire deep state strictly fixed at compile-time and that the object with this state will be considered frozen and completely immutable.
Can a method be static and final together in java? When we declare a method as final we can not override that method in sub class. In the same way when we declare a static method as final we can not hide it in sub class means we can not create same method in sub class.
final static declares a method which is static (can be called without an instance of the class) and final (can't be overridden by subclasses). static alone can be used to define a class-scoped variable, which isn't constant (but variables can't be final ).
Let's look at static variables and static methods first.
Class.variable
Class.methodName()
this
or super
keywords in anyway.Java also has "static nested classes". A static nested class is just one which doesn't implicitly have a reference to an instance of the outer class.
Static nested classes can have instance methods and static methods.
There's no such thing as a top-level static class in Java.
main method is
static
since it must be be accessible for an application to run before any instantiation takes place.
final
keyword is used in several different contexts to define an entity which cannot later be changed.A final
class cannot be subclassed. This is done for reasons of security and efficiency. Accordingly, many of the Java standard library classes are final
, for example java.lang.System
and java.lang.String
. All methods in a final
class are implicitly final
.
A final
method can't be overridden by subclasses. This is used to prevent unexpected behavior from a subclass altering a method that may be crucial to the function or consistency of the class.
A final
variable can only be initialized once, either via an initializer or an assignment statement. It does not need to be initialized at the point of declaration: this is called a blank final
variable. A blank final instance variable of a class must be definitely assigned at the end of every constructor of the class in which it is declared; similarly, a blank final static variable must be definitely assigned in a static initializer of the class in which it is declared; otherwise, a compile-time error occurs in both cases.
When an anonymous inner class is defined within the body of a method, all variables declared final
in the scope of that method are accessible from within the inner class. Once it has been assigned, the value of the final variable cannot change.
static means it belongs to the class not an instance, this means that there is only one copy of that variable/method shared between all instances of a particular Class.
public class MyClass {
public static int myVariable = 0;
}
//Now in some other code creating two instances of MyClass
//and altering the variable will affect all instances
MyClass instance1 = new MyClass();
MyClass instance2 = new MyClass();
MyClass.myVariable = 5; //This change is reflected in both instances
final is entirely unrelated, it is a way of defining a once only initialization. You can either initialize when defining the variable or within the constructor, nowhere else.
note A note on final methods and final classes, this is a way of explicitly stating that the method or class can not be overridden / extended respectively.
Extra Reading So on the topic of static, we were talking about the other uses it may have, it is sometimes used in static blocks. When using static variables it is sometimes necessary to set these variables up before using the class, but unfortunately you do not get a constructor. This is where the static keyword comes in.
public class MyClass {
public static List<String> cars = new ArrayList<String>();
static {
cars.add("Ferrari");
cars.add("Scoda");
}
}
public class TestClass {
public static void main(String args[]) {
System.out.println(MyClass.cars.get(0)); //This will print Ferrari
}
}
You must not get this confused with instance initializer blocks which are called before the constructor per instance.
The two really aren't similar. static
fields are fields that do not belong to any particular instance of a class.
class C {
public static int n = 42;
}
Here, the static
field n
isn't associated with any particular instance of C
but with the entire class in general (which is why C.n
can be used to access it). Can you still use an instance of C
to access n
? Yes - but it isn't considered particularly good practice.
final
on the other hand indicates that a particular variable cannot change after it is initialized.
class C {
public final int n = 42;
}
Here, n
cannot be re-assigned because it is final
. One other difference is that any variable can be declared final
, while not every variable can be declared static.
Also, classes can be declared final
which indicates that they cannot be extended:
final class C {}
class B extends C {} // error!
Similarly, methods can be declared final to indicate that they cannot be overriden by an extending class:
class C {
public final void foo() {}
}
class B extends C {
public void foo() {} // error!
}
static
means there is only one copy of the variable in memory shared by all instances of the class.
The final
keyword just means the value can't be changed. Without final
, any object can change the value of the variable.
final -
1)When we apply "final" keyword to a variable,the value of that variable remains constant. (or) Once we declare a variable as final.the value of that variable cannot be changed.
2)It is useful when a variable value does not change during the life time of a program
static -
1)when we apply "static" keyword to a variable ,it means it belongs to class.
2)When we apply "static" keyword to a method,it means the method can be accessed without creating any instance of the class
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With