I am using inheritance along with super function in my program ,but when I am extending my class it showing error message “There is no default constructor in ‘cc’. ” . This error message is coming after 1st subclass is extended and trying to make 2nd subclass. Here is the code Answer d…
Tag: inheritance
abstraction can be done without inheritance? java
Is abstraction possible without inheritance? This is my code Please note above, how i: did not extend the class “what” from abstract class “whatever” and yet the code runs perfectly with no errors Did not declare class “what” as abstract (since it’s not declaring the …
Extending the Graphics class in Java
I need to extend the Graphics class in order to @Override some methods including drawRect(int,int,int,int) and drawRoundRect(int,int,int,int,int,int). However, I have no idea how to do that. This is what I’ve got so far: I get an error on class declaration line saying: myGraphics is not abstract and doe…
Inheritance for builders in lombok
I was trying to use lombok for my project. I have a class A: and a class B: I am getting an error saying builder() in B cannot override builder() in A, as return type in BBuilder is not compatible with return type in ABuilder. Is there some way to do this using lombok? I do not want to write
Are static variables inherited
I have read at 1000’s of locations that Static variables are not inherited. But then how this code works fine? Parent.java Child.java This code prints “Parent”. Also read at few locations concept of data hiding. Parent.java Child.java Now the output is “Child”. So does this mean …
Java: how to have an array of subclass types?
Say I have a super class “Animal” and subclasses “Cat”, Dog, Bird”. Is there a way to have an array of subclass type rather than class instances with which I’ll be able to instantiate instances of each possible subclass? To simplify, I want this: How can I do that? Edit: I …
Initialize field before super constructor runs?
In Java, is there any way to initialize a field before the super constructor runs? Even the ugliest hacks I can come up with are rejected by the compiler: Note: The issue disappeared when I switched from inheritance to delegation, but I would still like to know. Answer No, there is no way to do this. Accordin…
Most efficient way to cast List to List
I have a List<SubClass> that I want to treat as a List<BaseClass>. It seems like it shouldn’t be a problem since casting a SubClass to a BaseClass is a snap, but my compiler complains that the cast is impossible. So, what’s the best way to get a reference to the same objects as a List&…
Java: Calling a super method which calls an overridden method
public class SuperClass { public void method1() { System.out.println(“superclass method1”); this.method2(); } public void method2() { System.out.println(“…
Calling super super class method
Let’s say I have three classes A, B and C. B extends A C extends B All have a public void foo() method defined. Now from C’s foo() method I want to invoke A’s foo() method (NOT its parent B’s method but the super super class A’s method). I tried super.super.foo();, but it’s…