java - Problems trying casting -

i've class extends textfield. class transform text uppercase , i'm trying casting class using beanfieldgroup doesn't work. using textfield works, class extends textfield doesn't.

/** class transfor text uppercase */ public class textupper extends textfield implements textchangelistener{      public textupper(integer length){         super();         setmaxlength(length);            setimmediate(true);         settextchangeeventmode(textchangeeventmode.eager);         addtextchangelistener(this);     }      public textupper(){         super();     }      @override     public void textchange(textchangeevent event) {         string text = event.gettext();         setvalue(text.touppercase());     } }   binder = new beanfieldgroup<mybean>(mybean.class); binder.setitemdatasource(ag); field<?> field = null;  field field = binder.buildandbind("name", "name"); // casting textupper textupper name = (textupper)binder.getfield("name"); form.addcomponent(name); 

any idea ???

i guess binder.getfield() returns textfield. after textupper name = (textupper)binder.getfield("name"); it'll still textfield, can check

name instanceof textupper 

the cast not change type. "i know textupper, special type of textfield", isn't, made like. if cast , call methods afterwards, object still call textfield's methods, , not textupper ones. have create new textupper, set the text (and other values) textfield , use object if want have behaviour.

or, use

buildandbind(string caption,                                         object propertyid,                                         class<t> fieldtype) 

with textupper :)

https://vaadin.com/download/prerelease/7.0/7.0.0/7.0.0.alpha3/docs/api/com/vaadin/data/fieldgroup/fieldgroup.html#buildandbind(java.lang.string, java.lang.object, java.lang.class)

---

try this:

 public textupper(integer length){         super();         setmaxlength(length);            setimmediate(true);         settextchangeeventmode(textchangeeventmode.eager);         addtextchangelistener(this);     }      public textupper(){         super();          setimmediate(true);         settextchangeeventmode(textchangeeventmode.eager);         addtextchangelistener(this);     } 

i have strong feeling buildandbind calls parameter less constructor, not put parameter length anywhere