abstract

Prevent Exposure of Base Classes (Abstract Classes)

由 旧城冷巷雨未停 提交于 2019-12-08 09:01:23
问题 So I looked through many related questions and none of them seem to fit all the way. At least not in my current understanding. As this is a simple issue, I'm going to be concise with my question and code. I have five classes: internal class A internal abstract class B : A internal abstract class C : B public class D : C public class E { public void X(C c) { } } There is an obvious accessibility issue here with the parameter C being used in a public method. I need to access class D without

ActionListener is abstract and does not override abstract method actionPerformed — despite containing that very method

由 核能气质少年 提交于 2019-12-08 07:00:25
问题 So I'm getting the error Class is not abstract and does not override abstract method actionPerformed(ActionEvent) in ActionListener I am aware of the origin of this error but what confuses me is that I have that method. public static ActionListener taskPerformer = new ActionListener(){ public void actionPerformed(ActionEvent e){ Clock cl = new Clock(); if(seconds<59){ seconds++; }else{ seconds=0; if(minutes<59){ minutes++; }else{ minutes=0; if(hours<12){ hours++; }else{ hours=0; } } } cl

Class must either be declared abstract or?

由 笑着哭i 提交于 2019-12-08 05:30:14
问题 I am new to android. I have always used snippets to create my app. So I copied material style drawer from this here. Now I am facing a problem in this part of the code: static class RecyclerTouchListener implements RecyclerView.OnItemTouchListener { private GestureDetector gestureDetector; private ClickListener clickListener; public RecyclerTouchListener(Context context, final RecyclerView recyclerView, final ClickListener clickListener) { this.clickListener = clickListener; gestureDetector =

“virtual” method's return type in objective-c

由 我们两清 提交于 2019-12-08 01:16:05
问题 I have a class which is supposed to be abstract. In one of it's abstract methods the return type may be an instance of class1,class2 or class3, depending on the class that's implementing the method. I'm wondering how should I declare the method in the abstract class. I thought about using dynamic typing, but I want the return type to be restricted to one of the 3 classes, not every type, and in addition I'm not sure I can override it so that in the inheriting class the return type will not

How to use generics and inherit from parent class without causing name clash?

由 耗尽温柔 提交于 2019-12-07 19:16:30
I have a parent class in Java called Flight . I have children classes: JetFlight , NormalFlight , etc. which inherit from Flight . I want all the children classes to implement compareTo from the Comparable interface. I want them to inherit from Flight because I want to use polymorphism (for example, initiate a Flight array and fill it with objects of JetFlight , NormalFlight , etc.). This is my code for the parent class: public abstract class Flight { public abstract int compareTo(Object o); } and this is the code for one of the children classes: public class JetFlight extends Flight

C++ and inheritance in abstract classes

由 泄露秘密 提交于 2019-12-07 15:17:20
问题 i have a problem in properly handling method overriding where an abstract class is present inside my classes hierarchy. I'll try to explain: class AbstractClass{ public: virtual void anyMethod() = 0; }; class A : public AbstractClass { void anyMethod() { // A implementation of anyMethod cout << "A"; } }; class B : public AbstractClass { void anyMethod() { // B implementation of anyMethod cout << "B"; } }; AbstractClass *ptrA, *ptrB; ptrA = new A(); ptrB = new B(); ptrA->anyMethod(); //prints

What is the difference between using <? extends SomeAbstract> vs. SomeAbstract in java generics

由 匆匆过客 提交于 2019-12-07 12:29:49
问题 I'm moving over to java from DotNet and this idea of extends is new. I've seen some posts that fully explain using List<? extends SomeAbstract> vs. List<? super SomeAbstract> vs. List<SomeAbstract> , but I'm guessing that there is no difference between using, and not using, extends in generics. Is that true? Would the answer change if using an abstract class as the parent? class My_AbstractExtends<T extends SomeAbstract> vs. class My_Abstract<SomeAbstract> EDIT Creates child classes as

Django OneToOneField to multiple models

由 ◇◆丶佛笑我妖孽 提交于 2019-12-07 10:20:31
问题 Suppose we have a base model: class BaseModel(models.Model): pass with some subclasses: class Submodel1(BaseModel): some_field = models.TextField() ... class Submodel9(BaseModel): another_field = models.TextField() Each submodel is defined in its own Django app. New apps with new submodels can appear. We also have another model, let's call it RelatedModel , which should have a one-to-one relation to BaseModel : class RelatedModel(models.Model): the_thing = models.OneToOneField(BaseModel, null

Can someone explain to me how this function works?

由 妖精的绣舞 提交于 2019-12-07 07:49:48
问题 I'm learning to code and I'm trying to understand Higher Order Functions and abstractions. I don't understand how this piece of code runs to return "true". function greaterThan(n) { return function(m) { return m > n; }; } var greaterThan10 = greaterThan(10); console.log(greaterThan10(11)); Thanks for the help. 回答1: The function greaterThan returns a function when called. The returned function has access to all the members of the outer function even after the function has returned. This is

Does an abstract property create a private backing field?

由 只谈情不闲聊 提交于 2019-12-07 06:44:55
问题 Simple question: does an abstract property create a private backing field? Example: public abstract Name { get; set; } Will this create a private backing field? I want to force any class that derives this property to use their own backing field, not one that's created by the compiler. 回答1: No it doesn't. I just tested with the following class: public abstract class Class1 { public abstract string TestStringAbstract { get; set; } public string TestString { get; set; } } and decompiled it in
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