This question already has answers here:
Why doesn't Java allow overriding of static methods?
(22 answers)
Closed 6 years ago.
Is this method type hiding? How static method gets area in memory?
public class Demo {
public static final void main(String args[]) {
try{
A a = new B();
a.display();
}catch(Exception e){
e.printStackTrace();
}
}
}
class A{
static void display(){
System.out.println("A");
}
}
class B extends A{
static void display(){
System.out.println("B");
}
}
Static methods dont belong to a instance but to a class, overriding some static method makes no sense and java will not let you to do that
Related
This question already has answers here:
Java order of Initialization and Instantiation
(2 answers)
What's wrong with overridable method calls in constructors?
(8 answers)
Closed 2 years ago.
class Main {
public static void main(String[] args) {
new B();
}
public static class A {
String f1 = "300";
public A(){
init();
}
protected void init(){}
}
public static class B extends A {
private String f1 = "3";
public B(){
super();
init();
}
protected void init(){
System.out.println(f1);
}
}
}
Output:
null
3
Can anyone explain to me the first line of the output? If I delete the line String f1 = "300";, it still has the same output also.
I have tried that if I declare some variables in B and invoke it in init() and all of it will be null in the constructor of A. In other words, my question is I want to know the reason for those variables being null at that point.
This question already has answers here:
What is the difference between a static method and a non-static method?
(13 answers)
Closed 4 years ago.
So, I'm pretty new to Java, and as far as I can see, both of these are the same things:
public class HelloWorld {
public void test(String test) {
System.out.println(test);
}
public static void main(String args[]) {
HelloWorld helloworld = new HelloWorld();
helloworld.test("Hello world!");
}
}
and
public class HelloWorld {
public static void test(String test) {
System.out.println(test);
}
public static void main(String args[]) {
test("Hello world!");
}
}
Are these both the same thing, and what's the reason you would use one over the other?
Static methods sometimes are difficult to test.
Non-static methods specify the behavior of objects. Static methods are typically for utility functions (such as Collections.sort())
This question already has answers here:
Are static methods inherited in Java?
(15 answers)
Closed 8 years ago.
I was able to run the following code:
class A
{
public static void display()
{
System.out.println("Inside static method of superclass");
}
}
class B extends A
{
public void show()
{
display();
}
}
public class staticMethodInheritance {
public static void main(String[] args) {
B b = new B();
b.display();
}
}
Now I was able to access the method display() from the instance of the class B then why is it said that static methods cannot be inherited. If I declare a method display in class B then it is said that the method in the superclass is hidden and the method in the child class is called then again isnt this the behavior that is desired when we override a method.
The only difference with inherited static (class) methods and inherited non-static (instance) methods is that when you write a new static method with the same signature, the old static method is just hidden, not overridden.
Static methods are inherited but cannot be overriden they can be re- defined.
This question already has answers here:
Static methods and their overriding
(5 answers)
Closed 8 years ago.
What should be printed when we execute this code?
I picked the question from here where the answer is provided but I kinda believe is wrong. First the call to a static function has to be done in static way, second when we override a static function the previous one is no longer accessible ( no new memory is assigned)
class Base {
public static void show() {
System.out.println("Base::show() called");
}
}
class Derived extends Base {
public static void show() {
System.out.println("Derived::show() called");
}
}
class Main {
public static void main(String[] args) {
Base b = new Derived();;
b.show();
}
}
static method belongs to class itself and overriding works for instance methods only. If you define the same method again in sub-class then it's called re-defining hiding of the static method.
static method looks for class to invoke it and that can be verified by below same code:
Base b = null;
b.show(); // Base::show() called
It doesn't make any sense to call static method via object.
This question already has answers here:
Can java call parent overridden method in other objects but not subtype?
(4 answers)
Closed 8 years ago.
Is there a way to call test() in class a from class b object created in class c ?
class a {
void test(){
System.out.println("in a");
}
}
class b extends a {
void test(){
System.out.println("in b");
}
}
public class c{
public static void main(String[] args) {
b refb = new b();
refb.test();
}
}
You can do that only within the test() method of class b like following.
class b extends a {
void test(){
super.test();
System.out.println("in b");
}
}
In Java, all non static private methods are virtual by default. So, there's no way to invoke a#test from b instance unless you modify b#test. The only way to do it (by your current design) is using an instance of a:
public class c{
public static void main(String[] args) {
b refb = new b();
// code to call test() in class a
//this is the only way you have in Java
a refA = new a();
a.test();
}
}