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extends

Generics in Java

I would like to understand the following type of syntax. Example: public interface A < T extends A < T> > { } What is the logic of this interface ?

2021-06-14 17:09:15    分类:问答    java   generics   interface   extends

Java Reflection getConstructor method

Lets say I have classes A and B, where B extends A. I also have a constructor in B with one argument which is of type A. I also have an object of type B called bObj. Is there a way to call B.class.getConstructor(new Class[] { bObj.getClass() }) and get the constructor since B extends A? At the moment I'm getting a NoSuchMethodException. Regards, Stan

2021-06-14 13:43:45    分类:问答    java   inheritance   reflection   extends   getconstructor

Java: Extending inner classes

I am trying to understand extending inner classes in Java. I have read around but nothing I found quite answers my question. So here goes... I have... public class Pie{ protected Slice[] slices; // Pie constructor public Pie(int n){ sliceGenerator(n) } private void sliceGenerator(int n){ slices = new Slice[n]; final float sweepAngle = 360.0f/(float)n; float startAngle = 0; for (int i=0;i<n;i++){ slices[i] = new Slice(startAngle); startAngle += sweepAngle; } } @Override public String toString(){ for (Slice s:slices){ s.toString(); } } // Inner class... public class Slice{ public Slice(float

2021-06-14 12:44:29    分类:问答    java   class   inheritance   extends

In Java type arguments, does <? extends E> mean strictly subtypes only? or would E also suffice?

In Java type arguments, does mean strictly subtypes only? or would E also suffice?

2021-06-14 09:45:02    分类:问答    java   generics   super   extends   bounded-types

Can you extend two classes in one class? [duplicate]

This question already has answers here: Closed 9 years ago. Possible Duplicate: Can I extend a class using more than 1 class in PHP? I have a class that has several child classes, however I am now adding another class which I also want to be a child of the parent, however I would also like to utilize many of the functions from one of the other child classes. I've thought of just moving the respective functions from the other child class to the parent, however didn't think this was really needed as it would only be these two child classes that make use of them so was hoping that I could extend

2021-06-13 20:08:02    分类:问答    php   oop   extends

What is the proper way to extend a class in another file?

This is what I have in foo.php class Foo { public $foo = NULL; public $foo2 = NULL; public function setFoo ($foo, $foo2) { $this->foo = $foo; $this->foo2 = $foo2' } } This is what I have in foo3.php class Foo3 extends Foo { public $foo3 = NULL; public function setFoo3 ($foo3) { $this->foo = $foo3; } } This is how I require it in my third file run.php: require_once "foo.php"; require_once "foo3.php"; $foo = new Foo(); $foo->setFoo3("hello"); I get this error: Fatal error: Call to undefined method Foo::setFoo3() I'm not sure if the problem is how I'm requiring them. Thanks.

2021-06-13 19:22:41    分类:问答    php   class   require   extends

差异为(Difference for <? super/extends String> in method and variable declaration)

问题 鉴于: import java.util.*; public class Hancock { //insert code here list.add("foo"); } } 哪两个在第 5 行独立插入的代码片段会在没有警告的情况下编译? (选择两项) A. public void addString(List list) { B. public void addString(List<String> list) { C. public void addString(List<? super String> list) { D. public void addString(List<? extends String> list) { 正确答案是 B 和 C。 答案 A 和 B 对我来说很清楚。 对于答案 C & D,我知道继承的方向,但是我不明白为什么答案 D 不能在 Eclipse 中编译,而所有其他答案都可以(A 带有关于泛型的警告,B & C 没有战争)。 Eclipse 中答案 D 的错误是The method add(capture#1-of ? extends String) in the type List<capture#1-of ? extends String> is not applicable for the arguments (String) The

2021-06-12 07:26:45    分类:技术分享    java   generics   collections   extends   super

Android:如何在扩展 Activity 的类中使用 onDraw 方法?(Android: How to use the onDraw method in a class extending Activity?)

问题 作为初学者,我一直在使用一个简单的布局 xml 和一个名为“Counter”的类构建一个简单的计数器应用程序,该类派生(扩展)自 Activity 类。 现在,我想加载一个位图(png 文件)以放置在计数器旁边。 我一直在阅读 onDraw(),但它需要该类来扩展“视图”。 我一直在尝试创建此类的一个对象来使用它,但无济于事。 我对这个概念有点困惑,如何轻松地做到这一点。 如果有人能解释一下,我将不胜感激。 回答1 使用 onDraw 函数的简单示例 - 它需要类来扩展视图 获取当前活动上下文的上下文 public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new myview(this)); } class myview extends View { public myview(Context context) { super(context); // TODO Auto-generated constructor stub } @Override protected void onDraw(Canvas

2021-06-11 10:27:27    分类:技术分享    android   android-activity   sdk   extends   ondraw

Using parent variables in a extended class in PHP

I have 2 classes, main and extended. I need to use main vars in extended class. <?php class Main { public $vars = array(); } $main = new Main; $main->vars['key'] = 'value'; class Extended extends Main { } $other = new Extended; var_dump($other->vars); ?> Who I can do it? No valid for example: <?php class Extended extends Main { function __construct ($main) { foreach ($main as $k => $v) { $this->$k = $v; } } } ?> I need some solution more transparent and efficient :)

2021-06-09 10:53:20    分类:问答    php   class   object   extends

Getting Bitmap from Custom SurfaceView

I have this code in a class that extends surface view and implements runnable I am able to use the class basically allows you to draw to the canvas using different colors and such. I'm trying to get a method that will allow me to save the image after it is drawn and this is the method. No matter what i do i just get a black image with nothing on it. Any ideas? I have cache drawing enabled Objective get a bitmap image from a custom SurfaceView I have exhausted options of looking at some other post on here and didn't find anything to work. Here is hoping that there is recently a new solution to

2021-06-05 03:48:19    分类:问答    android   bitmap   android-canvas   surfaceview   extends