adding an item to the JDT Refactor menu.

plugin.xml

<extension point="org.eclipse.ui.menus">
  <menuContribution locationURI="menu:org.eclipse.jdt.ui.refactoring.menu?after=typeGroup">
    <command
      commandId="mycommandid"
      label="mycommandlabel">
    </command>
  </menuContribution>
</extension>
<extension point="org.eclipse.ui.commands">
  <command
    id="mycommandid"
    name="mycommandname">
  </command>
</extension>
<extension point="org.eclipse.ui.handlers">
  <handler
    class="MyHandlerClass"
    commandId="mycommandid">
  </handler>
</extension>