Databases
StackOverflow2013
Postsdbo
POcan I reflectively instantiate a generic type in java?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POcan I reflectively instantiate a generic type in java?
    primarykey
    data
    text
    <p>Is it possible to reflectively instantiate a generic type in Java? Using the technique described <a href="http://www.velocityreviews.com/forums/t149816-generics-and-forname.html" rel="noreferrer">here</a> I get an error because class tokens cannot be generic. Take the example below. I want to instantiate some subclass of Creator that implements Creator. The actual class name is passed in as a command line argument. The idea is to be able to specify an implementation of Creator at runtime. Is there another way to accomplish what I'm trying to do here?</p> <pre><code>public interface Creator&lt;T&gt; { T create(); } public class StringCreator implements Creator&lt;String&gt; { public String create() { return new String(); } } public class FancyStringCreator implements Creator&lt;String&gt; { public String create() { return new StringBuffer().toString(); } } public static void main(String[] args) throws Exception { Class&lt;?&gt; someClass = Class.forName(args[0]); /*ERROR*/Class&lt;? extends Creator&lt;String&gt;&gt; creatorClass = someClass.asSubclass(Creator.class); Constructor&lt;? extends Creator&lt;String&gt;&gt; creatorCtor = creatorClass.getConstructor((Class&lt;?&gt;[]) null); Creator&lt;String&gt; creator = creatorCtor.newInstance((Object[]) null); } </code></pre> <p>Edit: I like Marcus' approach as being the most simple and pragmatic without circumventing the whole generics thing. I can use it in my situation because I can specify that the class passed must be a subclass of StringCreator. But as Ericson pointed out the generic information is still there at the type level, just not at the runtime level so it is still possible to reflectively examine whether a given class implements the correct generic type.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USsk.
    1. USsk.
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POcan I reflectively instantiate a generic type in java?
      1. USbruno conde
      1. VTFavorite
    2. VO
      singulars
      1. POcan I reflectively instantiate a generic type in java?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POcan I reflectively instantiate a generic type in java?
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

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