As the title suggests, I was wondering if there was a way to make my program execute the validation code in the constructor of my sub-class, instead of the validation code in the constructor in my parent class? Here is a very basic example: Here I have the constructor of my Teacher class, which throws an exce…
Tag: inheritance
ClassCastException “Parent cannot be cast to class…are in unnamed module of loader ‘app’ ” with Java Generics and inheritance
I´m currently facing a problem with generics in Java. I need to return a parent instance casted to the child. The sample below shows what I´m trying to achieve. This code does not run through and produces this exception instead: class com.generics.GenericTest$Parent cannot be cast to class com.generics.Generi…
The method compareTo(Comparable) is undefined for the type Comparable
So i am building a library as project that covers not all but most of the data structures and i found myself with this problem: At rows 40 and 41 (rows 3 and 4 of method containsKeyAux) it says “The method compareTo(Comparable) is undefined for the type Comparable” and this blows my mind cause the…
How do I define a field in a subclass by strictly following a given UML?
I’m trying to implement the UML diagram below using java: I only got recently exposed to UMLs and according to my understanding, I cannot set a field inside SBank or PBank to define their rate of interest. It can also be seen that in the class Bank there is no implementation for defining the rate of int…
Lombok with SuperBuilder
I have a Java project that uses Lombok ( a java library that automatically plugs into the editor and build tools ) and this one: but when I do the builder: I got this error: Answer Cannot reproduce. Check to make sure you’re on the latest lombok (currently, 1.18.16), and if that doesn’t solve the …
Difference between CustomTextView as Parent and Textview as Parent
i created CustomTextview as below . what is the difference between This and this When i put this TextView textView = findViewbyId(R.id.view); IDE runs without throwing error. Why? Thanks! Answer A real life comparison: When you learn to drive a manual transmission car, you can drive almost any manual transmis…
super.a = b instead of super(b)
I’m learning the super keyword and accidentally get this, here’s an example : The usual way to do this as in the tutorials is super(b) to reusing its parent constructor, but what is wrong with super.a = b? Answer When you write your class A like this: you overwrite the default constructor and in t…
How to increment numbers using Event Listeners and Widget Viewer in Java?
I’m writing a WidgetViewer GUI where when the “go up/up” button is pushed, a random number between 1 and 10 (inclusive) is generated and added to the left label, and another random number …
Using Inheritance like this is right?
I’m student learning Inheritance in Java. I’m making a program (Bitcoin Mining Game). In the program, there are different kind of digger (Mining Machine): ordinary digger (this only does digging coin), overclock digger (this can dig and can overclock to dig faster) and durability recover digger (t…
Accessing objects in other class Java inheritance
In my program I have class Vehicle and class Car which inherit from Vehicle. I’ve created two Car’s objects c and c2. Now I have to make sumFuel() method in Calculate class which sums fuel used by …