Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <blockquote> <p><em>what I want to know is why java forbids static fields/methods inside inner classes</em></p> </blockquote> <p>Because those inner classes are "instance" inner classes. That is, they are like an instance attribute of the enclosing object. </p> <p>Since they're "instance" classes, it doesn't make any sense to allow <code>static</code> features, for <code>static</code> is meant to work without an instance in the first place.</p> <p>It's like you try to create a static/instance attribute at the same time. </p> <p>Take the following example: </p> <pre><code>class Employee { public String name; } </code></pre> <p>If you create two instances of employee: </p> <pre><code>Employee a = new Employee(); a.name = "Oscar"; Employee b = new Employee(); b.name = "jcyang"; </code></pre> <p>It is clear why each one has its own value for the property <code>name</code>, right? </p> <p>The same happens with the inner class; each inner class instance is independent of the other inner class instance.</p> <p>So if you attempt to create a <code>counter</code> class attribute, there is no way to share that value across two different instances. </p> <pre><code>class Employee { public String name; class InnerData { static count; // ??? count of which ? a or b? } } </code></pre> <p>When you create the instance <code>a</code> and <code>b</code> in the example above, what would be a correct value for the static variable <code>count</code>? It is not possible to determine it, because the existence of the <code>InnerData</code> class depends completely on each of the enclosing objects. </p> <p>That's why, when the class is declared as <code>static</code>, it doesn't need anymore a living instance, to live itself. Now that there is no dependency, you may freely declare a static attribute.</p> <p>I think this sounds reiterative but if you think about the differences between instance vs. class attributes, it will make sense. </p>
    singulars
    1. This table or related slice is empty.
    1. POWhy does Java prohibit static fields in inner classes?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USOscarRyz
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI'll buy your explanation for static *properties* of the inner class, but as @skaffman points out in a comment to my answer, what about static *methods*? It seems as though methods should be allowed without mandating that they be detached from any instance. Indeed, in java, you can call static methods on instances (although it's considered bad style). BTW: I asked a colleague to attempt to compile the OP's code as C# and it *does* compile. So C# apparently allows this which demonstrates that what the OP wants to do doesn't violate some fundamental OO principle.
      singulars
      1. PO
      1. USAsaph
    2. COHappens exactly the same with the methods. The point here is not the *attributes* or the *methods* being statis or not, but the fact the inner class it self being **instance** "stuff". I mean, the problem here is that an instance of such inner class doesn't exists until the outer class is created. Hence what method would be dispatched then if there is nothing. You would hit air only because you'll need an instance in first place.
      singulars
      1. PO
      1. USOscarRyz
    3. COAbout C# ... well. It is not OO valid just because C# allows it, I don't mean it is wrong, but C# includes several paradigms to make the development easier even at cost of consistency ( you have to learn new things with each .NET release ) and it allows this and other kinds of things among others. I think that's a good thing. If the community feel an extra feature is cool enough C# may have it in the future.
      singulars
      1. PO
      1. USOscarRyz
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload