Thread-16" java.lang.UnsatisfiedLinkError: com/google/gwt/visualization/client/DataTable.create()

Hi I am trying to create a Datatable using Google Visualization client using java , i have following method to create a simple table chart , the code does not show any error , I have the out upput of the method to be written to a html file using stringbuffer but i am getting error as below , can someone please help me resolving the issue

Code :  public AbstractDataTable createTable() 

                {

                    DataTable data = DataTable.create();

                    data.addColumn(ColumnType.STRING, "Task");

                    data.addColumn(ColumnType.NUMBER, "Hours per Day");

                    data.addRows(2);

                    data.setValue(0, 0, "Work");

                    data.setValue(0, 1, 14);

                    data.setValue(1, 0, "Sleep");

                    data.setValue(1, 1, 10);

                    

                    return data;

                  }}

 Adding to html file using :  footer.append("<TD width='50%'><b><font color='#ff3333' face='Verdana' size=2>:"+ createTable() +"</b></font></TD>");

Error on run : Exception in thread "Thread-16" java.lang.UnsatisfiedLinkError: com/google/gwt/visualization/client/DataTable.create()Lcom/google/gwt/visualization/client/DataTable;

Thanks

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