Show a diff from action

From an action or wherever you like you can call this:

public void diff(final StreamSource local, final StreamSource remote){
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            try {
                DiffView view = Diff.getDefault().createDiff(local, remote);
                showDiff(view);
            } catch (IOException ex) {
                Logger.getLogger(ThisClass.class.getName()).throwing(ex);
            }
        }
    });
}
public void showDiff(final DiffView view){
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            //create our panel with our view
            //right now I am just going to use the diff component 
            // instead of a panel
            //create a topcomponent with our panel
            DiffTopComponent tc = new DiffTopComponent(view);
            tc.setName("MY_DIFF");
            tc.setDisplayName("Some display name");
            tc.open();
            tc.requestActive();
        }
    });
}

Embeded into TopComponent

Here is a top component to display it:

public class DiffTopComponent extends TopComponent {
    /** Creates a new instance of DiffTopComponent */
    public DiffTopComponent(Component diffPanel) {
        setLayout(new BorderLayout());
        add(diffPanel, BorderLayout.CENTER);
        getAccessibleContext().setAccessibleName(
            NbBundle.getMessage(DiffTopComponent.class, 
            "ACSN_Diff_Top_Component")); // NOI18N
        
        getAccessibleContext().setAccessibleDescription(
            NbBundle.getMessage(DiffTopComponent.class, 
            "ACSD_Diff_Top_Component")); // NOI18N
    }
   
    public DiffTopComponent(DiffView view) {
        this(view.getComponent());
    }
    public int getPersistenceType(){
        return TopComponent.PERSISTENCE_NEVER;
    }
    protected String preferredID(){
        return "DiffTopComponent";    //NOI18N
    }
    public HelpCtx getHelpCtx() {
        return new HelpCtx(getClass());
    }
}