You didn't override anything here. To see for yourself, Try putting @Override annotation before public static void a() in class B and Java will throw an error.
You just defined a function in class B called a(), which is distinct (no relation whatsoever) from the function a() in class A.
But Because B.a() has the same name as a function in the parent class, it hides A.a() [As pointed by Eng. Fouad]. At runtime, the compiler uses the actual class of the declared reference to determine which method to run. For example,
B b = new B();
b.a() //prints B.a()
A a = (A)b;
a.a() //print A.a(). Uses the declared reference's class to find the method.
You cannot override static methods in Java. Remember static methods and fields are associated with the class, not with the objects. (Although, in some languages like Smalltalk, this is possible).
I found some good answers here: Why doesn't Java allow overriding of static methods?
That's called hiding a method, as stated in the Java tutorial Overriding and Hiding Methods:
If a subclass defines a class method with the same signature as a class method in the superclass, the method in the subclass hides the one in the superclass.
You didn't override the method a(), because static methods are not inherited. If you had put @Override, you would have seen an error.
A.java:10: error: method does not override or implement a method from a supertype
@Override
^
1 error
But that doesn't stop you from defining static methods with the same signature in both classes.
Also, the choice of method to call depends on the declared type of the variable.
B b = null;
b.a(); // (1) prints B.a()
A a = new B();
a.a(); // (2) prints a.a()
At (1), if the system cared about the identity of b, it would throw a NPE. and at (2), the value of a is ignored. Since a is declared as an A, A.a() is called.
While goblinjuice answer was accepted, I thought the example code could improved:
public class StaticTest {
public static void main(String[] args) {
A.print();
B.print();
System.out.println("-");
A a = new A();
B b = new B();
a.print();
b.print();
System.out.println("-");
A c = b;
c.print();
}
}
class A {
public static void print() {
System.out.println("A");
}
}
class B extends A {
public static void print() {
System.out.println("B");
}
}
Produces:
A
B
-
A
B
-
A
If B had overridden print() it would have write B on the final line.
Static methods will called by its Class name so we don't need to create class object we just cal it with class name so we can't override static
for example
class AClass{
public static void test(){
}
}
class BClass extends AClass{
public static void test(){}
}
class CClass extends BClass{
public static void main(String args[]){
AClass aclass=new AClass();
aclass.test(); // its wrong because static method is called
// by its class name it can't accept object
}
}
we just call it
AClass.test();
means static class can't be overridden if it's overridden then how to cal it .
B.a()is only accessible via classB. If you have something likeA a = new B(); a.a();, it will print "A.a()", even though it's of type B. If it were truly overridden, then it would have printed "B.a()". Note that it is Java's odd feature that allows you to call static methods from an object instance that helps sow confusion here. – dlevainsideB? You can test that easily by adding@Overrideannotation before that method. – Pshemoa()is inherited byBif you remove thea()function fromB. It does inherit, but it does not override. Instead it hidesa()if you declare anothera()function inB. – Dorus