I was pretty excited to find UiHandler, it makes the organization of code so much cleaner!

I am putting in the full code for both, so you can see the beauty for yourself! Pay attention to the comments where i put the gotchas that got me at first! :)
Before:

PLAIN TEXT
JAVA:
  1. package com.rubygeek.sandbox.client;
  2.  
  3. import java.util.ArrayList;
  4.  
  5. import com.google.gwt.core.client.GWT;
  6. import com.google.gwt.event.dom.client.ClickEvent;
  7. import com.google.gwt.event.dom.client.ClickHandler;
  8. import com.google.gwt.uibinder.client.UiBinder;
  9. import com.google.gwt.uibinder.client.UiField;
  10. import com.google.gwt.user.client.Window;
  11. import com.google.gwt.user.client.ui.Button;
  12. import com.google.gwt.user.client.ui.CheckBox;
  13. import com.google.gwt.user.client.ui.Composite;
  14. import com.google.gwt.user.client.ui.Widget;
  15.  
  16.  
  17. public class LanguageList extends Composite {
  18.  
  19.   interface MyUiBinder extends UiBinder<Widget, LanguageList> {}
  20.   private static MyUiBinder uiBinder = GWT.create(MyUiBinder.class);
  21.  
  22.   @UiField CheckBox rubyCheck;
  23.   @UiField CheckBox pythonCheck;
  24.   @UiField CheckBox javaCheck;
  25.   @UiField CheckBox phpCheck;
  26.   @UiField Button button;
  27.  
  28.   public LanguageList() {
  29. // bind XML file of same name of this class to this class
  30. initWidget(uiBinder.createAndBindUi(this));
  31.  
  32. final ArrayList<CheckBox> boxes = new ArrayList<CheckBox>();
  33. boxes.add(rubyCheck);
  34. boxes.add(pythonCheck);
  35. boxes.add(javaCheck);
  36. boxes.add(phpCheck);
  37.  
  38. // add button and handler to alert the values of checkboxes
  39. button.addClickHandler(new ClickHandler() {
  40. public void onClick(ClickEvent event) {
  41. String output = "";
  42. for(CheckBox box : boxes) {
  43. if (box.getValue()) {
  44. output += box.getFormValue() + ", ";
  45. }
  46. }
  47. Window.alert("You checked: "+ output);
  48. }
  49. });
  50.  
  51.   }
  52. }

After:

PLAIN TEXT
JAVA:
  1. package com.rubygeek.sandbox.client;
  2.  
  3. import java.util.ArrayList;
  4.  
  5. import com.google.gwt.core.client.GWT;
  6. import com.google.gwt.event.dom.client.ClickEvent;
  7. import com.google.gwt.uibinder.client.UiBinder;
  8. import com.google.gwt.uibinder.client.UiField;
  9. import com.google.gwt.uibinder.client.UiHandler;
  10. import com.google.gwt.user.client.Window;
  11. import com.google.gwt.user.client.ui.CheckBox;
  12. import com.google.gwt.user.client.ui.Composite;
  13. import com.google.gwt.user.client.ui.Widget;
  14.  
  15. public class LanguageList extends Composite {
  16.  
  17.   interface MyUiBinder extends UiBinder<Widget, LanguageList> {}
  18.   private static MyUiBinder uiBinder = GWT.create(MyUiBinder.class);
  19.  
  20.   final ArrayList<CheckBox> boxes = new ArrayList<CheckBox>();
  21.  
  22.   @UiField CheckBox rubyCheck;
  23.   @UiField CheckBox pythonCheck;
  24.   @UiField CheckBox javaCheck;
  25.   @UiField CheckBox phpCheck;
  26.  
  27.   // add ClickEvent handler to button with ui:field="languageButton" in the UiBinder code    
  28.   // !!! note no ; at end of this annotation, and the name of function does not matter, its the annotation that ties it to the
  29.   // body of the method, also this does not go inside the class :) (i spend 40 mins figuring that out...)
  30.   @UiHandler("languageButton")
  31.   void doClick(ClickEvent event) {
  32.       String output = "";
  33.       for(CheckBox box : boxes) {
  34.           if (box.getValue()) {
  35.               output += box.getFormValue() + ", ";
  36.           }
  37.       }
  38.       Window.alert("You checked: "+ output);
  39.  }
  40.  
  41.   public LanguageList() {
  42.       // bind XML file of same name of this class to this class
  43.       initWidget(uiBinder.createAndBindUi(this));
  44.       
  45.       boxes.add(rubyCheck);
  46.       boxes.add(pythonCheck);
  47.       boxes.add(javaCheck);
  48.       boxes.add(phpCheck);
  49.   }
  50. }

See the constructure is further slimmed down!