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Java Forum / General / September 2007Importing an object at runtime
Class theClass = Class.forName("Object1"); Object1 o = theClass.newInstance(); ((Object1)o).go(); I need to wrap the object as an Object1 to be able to call go(). If I am reading the classes from disk and don't hardcode the classes into Class.forName("????") how do I then wrap the resulting object? Something like this: Class theClass = Class.forName(file); Object o = theClass.newInstance(); ((obj.getClass().getName())o).go(); //can't do obj.getClass().getName() > Class theClass = Class.forName("Object1"); > Object1 o = theClass.newInstance(); > ((Object1)o).go(); Why not simply this way? Object1 o = new Object1(); o.go();  SignatureThomas On Thu, 30 Aug 2007 18:20:14 GMT, Thomas Fritsch <i.dont.like.spam@invalid.com> wrote, quoted or indirectly quoted someone who said : >> Class theClass = Class.forName("Object1"); >> Object1 o = theClass.newInstance(); >> ((Object1)o).go(); >Why not simply this way? > Object1 o = new Object1(); > o.go(); If he knew the name of Object1 at compile time he would not need to dick around with Class.forName. You only need this whacky stuff when you don't know the name of the class at compile time. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com On Aug 30, 11:07 am, "Crouchez" <b...@bllllllahblllbllahblahblahhh.com> wrote: > Class theClass = Class.forName("Object1"); > Object1 o = theClass.newInstance(); [quoted text clipped - 9 lines] > Object o = theClass.newInstance(); > ((obj.getClass().getName())o).go(); //can't do obj.getClass().getName() How are you sure that "go()" is implemenented by the object you're trying to instantiate? I believe this can be done in a cleaner way, where you instantiate the object, and use instanceOf to make sure the instance is implementing the interface which has "go()", cast it as that interface (which is allowed) and then call the method go() on it. -cheers, Manish > On Aug 30, 11:07 am, "Crouchez" > <b...@bllllllahblllbllahblahblahhh.com> wrote: [quoted text clipped - 17 lines] > instance is implementing the interface which has "go()", cast it as > that interface (which is allowed) and then call the method go() on it. Example: public interface Goer { public void go(); } public class DoesGo implements Goer { public void go() { ... } } ... // inside some other method or class: Goer goer = new DoesGo(); // can also instantiate with // Class<? extends Goer>.forName( "DoesGo" ).newInstance)); SignatureLew On Thu, 30 Aug 2007 18:07:51 GMT, "Crouchez" <blah@bllllllahblllbllahblahblahhh.com> wrote, quoted or indirectly quoted someone who said : >I need to wrap the object as an Object1 to be able to call go(). If I am >reading the classes from disk and don't hardcode the classes into >Class.forName("????") how do I then wrap the resulting object? Normally your dynamic class will implement an interface. You can then cast the object to that interface and call its method. See http://mindprod.com/jgloss/classforname.html Failing that, you get bogged in the horrors of introspection/reflection. see http://mindprod.com/jgloss/reflection.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > On Thu, 30 Aug 2007 18:07:51 GMT, "Crouchez" > <blah@bllllllahblllbllahblahblahhh.com> wrote, quoted or indirectly [quoted text clipped - 8 lines] > > See http://mindprod.com/jgloss/classforname.html I can't the interface's method is protected. On Sep 1, 10:07 pm, "Crouchez" <b...@bllllllahblllbllahblahblahhh.com> wrote: > I can't the interface's method is protected. Why/How is the interface's method protected? AFAIK, you cannot even compile an interface with a protected method. You can have default (none), public or abstract modifiers only. -cheers, Manish "Crouchez" wrote, quoted or indirectly quoted someone who said: >>> I need to wrap the object as an Object1 to be able to call go(). If I am >>> reading the classes from disk and don't hardcode the classes into >>> Class.forName("????") how do I then wrap the resulting object? "Roedy Green" wrote: >> Normally your dynamic class will implement an interface. You can then >> cast the object to that interface and call its method. >> >> See http://mindprod.com/jgloss/classforname.html Crouchez wrote: > I can't the interface's method is protected. > AFAIK, you cannot even compile an interface with a protected method. > You can have default (none), public or abstract modifiers only. All interface methods are public abstract. You may redundantly declare them so, but you may not contradict these modifiers. They are never package-private. <http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html#9.1.5> > All interface members are implicitly public. <http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html#9.4> > Every method declaration in the body of an interface is implicitly abstract, so its body is always represented by a semicolon, not a block. > > Every method declaration in the body of an interface is implicitly public. So, Crouchez, what is the difficulty? SignatureLew Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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