Error loading google maps v3 in gwt - google-maps

Question

I am searching for a library to visualize data as glyphs over a map. Therefore I thought of using google maps api v3 in gwt and dwar the glyohs as an overlay overlay.
Unfortunately I couldn't find any working sample code to get started.
I followed this tutorial
and while executing the project I got this Error:
Unable to load module entry point
classcom.example.google.gwt.mapstutorial.client.SimpleMaps (see associated exception or
details)
java.lang.RuntimeException: Deferred binding failed for
'com.google.gwt.maps.client.impl.MapOptionsImpl' (did you forget to inherit a required module?)
at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:53)
at com.google.gwt.core.client.GWT.create(GWT.java:97)
at com.google.gwt.maps.client.impl.MapOptionsImpl.<clinit>(MapOptionsImpl.java:31)
at com.google.gwt.maps.client.MapOptions.<init>(MapOptions.java:40)
at com.example.google.gwt.mapstutorial.client.SimpleMaps.onModuleLoad(SimpleMaps.java:15)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.ModuleSpace.onLoad(ModuleSpace.java:396)
at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:525)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
at java.lang.Thread.run(Unknown Source)Caused by: java.lang.IncompatibleClassChangeError: Found interface com.google.gwt.core.ext.typeinfo.JClassType, but class was expected
at com.google.gwt.jsio.rebind.JSWrapperGenerator.generate(JSWrapperGenerator.java:276)
at com.google.gwt.core.ext.GeneratorExtWrapper.generate(GeneratorExtWrapper.java:48)
at com.google.gwt.core.ext.GeneratorExtWrapper.generateIncrementally(GeneratorExtWrapper.java:60)
at com.google.gwt.dev.javac.StandardGeneratorContext.runGeneratorIncrementally(StandardGeneratorContext.java:647)
at com.google.gwt.dev.cfg.RuleGenerateWith.realize(RuleGenerateWith.java:41)
at com.google.gwt.dev.shell.StandardRebindOracle$Rebinder.rebind(StandardRebindOracle.java:78)
at com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:268)
at com.google.gwt.dev.shell.ShellModuleSpaceHost.rebind(ShellModuleSpaceHost.java:141)
at com.google.gwt.dev.shell.ModuleSpace.rebind(ModuleSpace.java:585)
at com.google.gwt.dev.shell.ModuleSpace.rebindAndCreate(ModuleSpace.java:455)
at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:49)
at com.google.gwt.core.client.GWT.create(GWT.java:97)
at com.google.gwt.maps.client.impl.MapOptionsImpl.<clinit>(MapOptionsImpl.java:31)
at com.google.gwt.maps.client.MapOptions.<init>(MapOptions.java:40)
at com.example.google.gwt.mapstutorial.client.SimpleMaps.onModuleLoad(SimpleMaps.java:15)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.ModuleSpace.onLoad(ModuleSpace.java:396)
at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:525)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
at java.lang.Thread.run(Unknown Source)
Could anyone help me out here, or does anyone has another suggestion for a library to use in gwt, thanks!
Here is my Code:
package com.example.google.gwt.mapstutorial.client;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.maps.client.MapOptions;
import com.google.gwt.maps.client.MapTypeId;
import com.google.gwt.maps.client.MapWidget;
import com.google.gwt.maps.client.base.LatLng;
import com.google.gwt.user.client.ui.RootPanel;
public class SimpleMaps implements EntryPoint {
private MapWidget mapWidget;
// GWT module entry point method.
public void onModuleLoad() {
final MapOptions options = new MapOptions();
// Zoom level. Required
options.setZoom(8);
// Open a map centered on Cawker City, KS USA. Required
options.setCenter(new LatLng(39.509, -98.434));
// Map type. Required.
options.setMapTypeId(new MapTypeId().getRoadmap());
// Enable maps drag feature. Disabled by default.
options.setDraggable(true);
// Enable and add default navigation control. Disabled by default.
options.setNavigationControl(true);
// Enable and add map type control. Disabled by default.
options.setMapTypeControl(true);
mapWidget = new MapWidget(options);
mapWidget.setSize("800px", "600px");
// Add the map to the HTML host page
RootPanel.get("mapsTutorial").add(mapWidget);
}
}