This is code for Making tree in GWT and by this we are also calling "write.java" in which "RICHTEXTEDITOR's" coding exists...

 
package com.client;

import com.google.gwt.user.client.ui.Button;


public class EnggHeads  {
    RootPanel rt;
    AbsolutePanel absolutePanel_left;
    AbsolutePanel absolutePanel_right;
  
    public EnggHeads() {
        rt=RootPanel.get();
        HorizontalSplitPanel horizontalSplitPanel = new HorizontalSplitPanel();
      
        rt.add(horizontalSplitPanel, 0, 0);
        horizontalSplitPanel.setSize("1000px", "1000px");
      
        horizontalSplitPanel.setSplitPosition("150");
      
        absolutePanel_right = new AbsolutePanel();
        horizontalSplitPanel.setRightWidget(absolutePanel_right);
        absolutePanel_right.setSize("100%", "590px");
      
        AbsolutePanel absolutePanel_left = new AbsolutePanel();
        horizontalSplitPanel.setLeftWidget(absolutePanel_left);
        absolutePanel_left.setSize("100%", "100%");
      
        TreeItem root = new TreeItem("Research Paper");
        root.setHeight("124px");
        Hyperlink hyper_upload=new Hyperlink("Upload", false, "newHistoryToken");
        hyper_upload.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                absolutePanel_right.clear();
                FileUploader1 f= new FileUploader1();
                f.setVisible(true);
              
            }
        });
        root.addItem(hyper_upload);
      Hyperlink hh= new Hyperlink("Write", false, "newHistoryToken");
       hh.addClickHandler(new ClickHandler() {
      
        @Override
        public void onClick(ClickEvent event) {
            // TODO Auto-generated method stub
            absolutePanel_right.clear();
            Write ff=new Write();   //This is calling of the class write in which richtexteditor code exists
            ff.setVisible(true);
        }
    });
       root.addItem(hh);
        Tree t = new Tree();
        t.addItem(root);
        root.setState(true);
      
        absolutePanel_left.add(t);
    }
}


Step2:-
  Make a folder images in war folder of your project and inser these below listed icons in that--
http://scripts.ringsworld.com/news-publishing/easynews17/icons/bold.gif.html
http://scripts.ringsworld.com/news-publishing/easynews17/icons/italic.gif.html
http://scripts.ringsworld.com/news-publishing/easynews17/icons/underline.gif.html
http://s613.photobucket.com/albums/tt219/brakesk8/?action=view&current=justifycenter.gif&newest=1
http://s610.photobucket.com/albums/tt189/tonybee9119/icon/?action=view&current=justifyright.gif&currenttag=icon


Step3:- Now after saving these images make another file "write.java"


package com.client;

import java.io.File;
import java.io.IOException;

import org.eclipse.swt.internal.win32.CREATESTRUCT;

import com.gargoylesoftware.htmlunit.javascript.host.Window;
import com.google.gwt.event.dom.client.ChangeHandler;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.RichTextArea;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.AbsolutePanel;
import com.google.gwt.user.client.ui.ListBox;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.RichTextArea.ExtendedFormatter;
import com.gwtext.client.widgets.Toolbar;
import com.gwtext.client.widgets.ToolbarButton;
import com.gwtext.client.widgets.event.ButtonListenerAdapter;
import com.google.gwt.event.dom.client.ChangeEvent;
import com.gwtext.client.core.EventObject;
import com.google.gwt.user.datepicker.client.DateBox;
import com.gwtext.client.widgets.form.TimeField;
import com.google.gwt.user.datepicker.client.DateBox.DefaultFormat;
import com.google.gwt.i18n.client.DateTimeFormat;

@SuppressWarnings("deprecation")
public class Write extends Composite {
    RootPanel rootpanel;
    AbsolutePanel absolutePanel;
    Label stream;
    ListBox streamvalue ;
    Label subject;
    ListBox subjectvalue;
    Label lblTypeAProblem;
    RichTextArea richTextArea;
    ExtendedFormatter formatter;
      Toolbar tt;
     
      ToolbarButton bold;
      ToolbarButton italic;
      ToolbarButton underline;
      ToolbarButton  leftjustification;
      ToolbarButton  rightjustification;
      ToolbarButton  centerjustification;
   
      ListBox fontsize;
    public Write() {
   
        rootpanel=RootPanel.get();

        absolutePanel = new AbsolutePanel();
        rootpanel.add(absolutePanel, 191, -4);
        absolutePanel.setSize("450px", "382px");
        stream = new Label("Stream");
        absolutePanel.add(stream, 201, 22);
        richTextArea = new RichTextArea();
        absolutePanel.add(richTextArea, 86, 170);
        richTextArea.setSize("354px", "98px");

        formatter=richTextArea.getExtendedFormatter();
        tt=new Toolbar();

        absolutePanel.add(tt, 88, 130);
        tt.setSize("351px", "31px");
       
        fontsize = new ListBox();

        absolutePanel.add(fontsize, 244, 134);
        fontsize.setSize("35px", "27px");
        fontsize.addItem("1");
        fontsize.addItem("2");
        fontsize.addItem("3");
        fontsize.addItem("4");
        fontsize.addItem("5");
        fontsize.addItem("6");
        fontsize.addItem("7");


        // tglbtnB = new ToggleButton("B");

         bold=new ToolbarButton();
        //bold.setToggleGroup("");
        bold.setText("");
        bold.setTooltip("Bold");
        bold.setCls("button");
        bold.setToggleGroup("format");
        bold.setIconCls("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/bold.gif");
       
        tt.addButton(bold);
        bold.setSize("34px", "30px");



        italic=new ToolbarButton();
        italic.setText("");
        italic.setTooltip("Italic");
        italic.setToggleGroup("format");
        italic.setIcon("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/italic.gif");

        tt.addButton(italic);



        underline=new ToolbarButton();
        underline.setText("");
        underline.setToggleGroup("format");
        underline.setIcon("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/underline.gif");
        tt.addButton(underline);



        leftjustification=new ToolbarButton();
        leftjustification.setToggleGroup("justification");
        leftjustification.setTooltip("left");
        leftjustification.setText("");
        leftjustification.setIcon("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/justifyleft.gif");

        tt.addButton(leftjustification);


        centerjustification=new ToolbarButton();
        centerjustification.setToggleGroup("justification");
        centerjustification.setText("");
        centerjustification.setIcon("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/justifyCenter.gif");
        centerjustification.setTooltip("Center");

        tt.addButton(centerjustification);

        rightjustification=new ToolbarButton();
        rightjustification.setToggleGroup("justification");
        rightjustification.setText("");
        rightjustification.setIcon("G:/gwt-2.0.4/gwt-2.0.4/logcom/war/images/justifyRight.gif");
        rightjustification.setTooltip("Right");

        tt.addButton(rightjustification);
       
       
        DateBox dateBox = new DateBox();
        dateBox.setFormat(new DefaultFormat(DateTimeFormat.getFullDateFormat()));
        absolutePanel.add(dateBox, 177, 549);
        dateBox.setSize("98px", "23px");
       
       
        Label lblEnterDatetime = new Label("Enter Date/Time");
        absolutePanel.add(lblEnterDatetime, 56, 549);
        TimeField timeField = new TimeField("New time field", "time_field", 100);
        absolutePanel.add(timeField, 298, 548);
       
        Label lblTitle = new Label("Title");
        absolutePanel.add(lblTitle, 119, 52);
        lblTitle.setSize("254px", "18px");
       
        final TextBox txtbxTitle = new TextBox();
        txtbxTitle.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                txtbxTitle.setText("");
            }
        });
        txtbxTitle.setText("Title");
        absolutePanel.add(txtbxTitle, 257, 46);
        txtbxTitle.setSize("166px", "16px");
       
        Label lblAuthor = new Label("Author");
        absolutePanel.add(lblAuthor, 124, 82);
        lblAuthor.setSize("257px", "18px");
       
        final TextBox txtbxAuthorName = new TextBox();
        txtbxAuthorName.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
               
                txtbxAuthorName.setText("");
            }
        });
        txtbxAuthorName.setText("Author name");
        absolutePanel.add(txtbxAuthorName, 260, 80);
        txtbxAuthorName.setSize("163px", "16px");
       
        Button button_1 = new Button("New button");
        button_1.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
            String ss=richTextArea.getText();
            String st=txtbxTitle.getText();
            String sa=txtbxAuthorName.getText();
        com.google.gwt.user.client.Window.alert(ss);
       
            }
        });
        button_1.setText("Submit");
        absolutePanel.add(button_1, 213, 274);
        button_1.setSize("100px", "28px");






        bold.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
            //richTextArea.setHTML("<b></b>");
           
            formatter.toggleBold();
            }
        });

        italic.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
           
            formatter.toggleItalic();
            }
        });


        underline.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
            formatter.toggleUnderline();
            }
        });




        leftjustification.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
           
            formatter.setJustification(RichTextArea.Justification.LEFT);
            }
        });



        centerjustification.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
                formatter.setJustification(RichTextArea.Justification.CENTER);
            }
        });


        rightjustification.addListener(new ButtonListenerAdapter() {
            public void onClick(com.gwtext.client.widgets.Button button, EventObject e) {
                formatter.setJustification(RichTextArea.Justification.RIGHT);
            }
        });



        fontsize.addChangeHandler(new ChangeHandler() {
            public void onChange(ChangeEvent event) {
                if(fontsize.isItemSelected(0))
            formatter.setFontSize(RichTextArea.FontSize.XX_SMALL);
               
                if(fontsize.isItemSelected(1))
                    formatter.setFontSize(RichTextArea.FontSize.X_SMALL);

                if(fontsize.isItemSelected(2))
                    formatter.setFontSize(RichTextArea.FontSize.SMALL);

                if(fontsize.isItemSelected(3))
                    formatter.setFontSize(RichTextArea.FontSize.MEDIUM);

                if(fontsize.isItemSelected(4))
                    formatter.setFontSize(RichTextArea.FontSize.LARGE);

                if(fontsize.isItemSelected(5))
                    formatter.setFontSize(RichTextArea.FontSize.X_LARGE);

                if(fontsize.isItemSelected(6))
                    formatter.setFontSize(RichTextArea.FontSize.XX_LARGE);

               

               
            }
        });   
       
    }
}


This is all about richtexteditor in gwt.You can also add additional functions in it as per your requirement..

Thanks for your attentions...

Vishal Dixit,Sonal Garg