Why does the code below create the gap between containers when the form is built?

I am using the following code:

        Container resp = new Container(BoxLayout.y());
//        TextField sl = new TextField();
        Label sl = new Label(recnopr);
        sl.setUIID("textLarge");
        Label sl2 = new Label(sesname1);
        sl2.setUIID("textLarge");
        Label sl3 = new Label("Session Name:");
        sl3.setUIID("textLarge");
        Container c1 = new Container();
        c1.add(licon);
        Container c2 = new Container();
        c2.add(sl);
        Container c3 = new Container();
        c3.add(sl3);
        Container c4 = new Container();
        c4.add(sl2);
        TableLayout tli = new TableLayout(1, 4);
        Container icn = new Container(tli);//icn exnmelb exnmetf
        icn.add(tli.createConstraint().widthPercentage(20), c1).
                add(tli.createConstraint().widthPercentage(43).verticalAlign(Component.CENTER), c2).
                add(tli.createConstraint().widthPercentage(21).verticalAlign(Component.CENTER), c3).
                add(tli.createConstraint().widthPercentage(16).verticalAlign(Component.CENTER), c4);
        resp.add(icn);
        //Session 1
        Label sl4 = new Label("Session Objective:  ");
        sl4.setUIID("textLarge");
        TextArea line2 = new TextArea(2, 30, TextArea.ANY);
        line2.setUIID("textfieldLarge");
        Container c5 = new Container();
        c5.add(sl4).add(line2);
        resp.add(c5);
        // Exercise 1
        SpanLabel sl5  = new SpanLabel("Exercise #1 Set Up and Description: ");
        sl5.setTextUIID("textMedium");
        TextArea line3 = new TextArea(2, 20, TextArea.ANY);
        line3.setUIID("textfieldLarge");
        TableLayout tlii = new TableLayout(1, 2);
        String line4t = pr.line4.get();
        Button l4 = new Button("Demonstrate:      " + line4t);
        l4.setUIID("textMedium");
        Container e1 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        e1.add(sl5).add(l4);
        Container c6 = new Container(tlii);
        c6.add(tlii.createConstraint().widthPercentage(40), e1).
                add(tlii.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line3);
        resp.add(c6);
        // Exercise 2
        SpanLabel sl6  = new SpanLabel("Exercise #2 Set Up and Description: ");
        sl6.setTextUIID("textMedium");
        TextArea line5 = new TextArea(2, 20, TextArea.ANY);
        line5.setUIID("textfieldLarge");
        TableLayout tliii = new TableLayout(1, 2);
        String line6t = pr.line6.get();
        Button l6 = new Button("Demonstrate:      " + line6t);
        l6.setUIID("textMedium");
        Container e2 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        e2.add(sl6).add(l6);
        Container c7 = new Container(tliii);
        c7.add(tliii.createConstraint().widthPercentage(40), e2).
                add(tliii.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line5);
        resp.add(c7);
        //Exercise 3
        SpanLabel sl7  = new SpanLabel("Exercise #3 Set Up and Description: ");
        sl7.setTextUIID("textMedium");
        TextArea line7 = new TextArea(2, 20, TextArea.ANY);
        line7.setUIID("textfieldLarge");
        TableLayout tliv = new TableLayout(1, 2);
        String line8t = pr.line8.get();
        Button l7 = new Button("Demonstrate:      " + line8t);
        l7.setUIID("textMedium");
        Container e3 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        e3.add(sl7).add(l7);
        Container c8 = new Container(tliv);
        c8.add(tliv.createConstraint().widthPercentage(40), e3).
                add(tliv.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line7);
        resp.add(c8);
        //Excersize 4
        SpanLabel sl8  = new SpanLabel("Exercise #4 Set Up and Description: ");
        sl8.setTextUIID("textMedium");
        TextArea line9 = new TextArea(2, 20, TextArea.ANY);
        line9.setUIID("textfieldLarge");
        Container e4 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        e4.add(sl8);
        TableLayout tlv = new TableLayout(1, 2);
        Container c9 = new Container(tlv);
        c9.add(tlv.createConstraint().widthPercentage(40), e4).
                add(tlv.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line9);resp.add(c9);
        //Exercise 5
        SpanLabel sl9  = new SpanLabel("Exercise #5 Set Up and Description: ");
        sl9.setTextUIID("textMedium");
        TextArea line10 = new TextArea(2, 20, TextArea.ANY);
        line10.setUIID("textfieldLarge");
        Container e5 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        TableLayout tlvi = new TableLayout(1, 2);
        e5.add(sl9);
        Container c10 = new Container(tlvi);
        c10.add(tlvi.createConstraint().widthPercentage(40), e5).
                add(tlvi.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line10);
        resp.add(c10);
        // Exercise 6
        SpanLabel sl11  = new SpanLabel("Exercise #6 Set Up and Description: ");
        sl11.setTextUIID("textMedium");
        TextArea line11 = new TextArea(2, 20, TextArea.ANY);
        Container e6 = new Container(new BoxLayout(BoxLayout.Y_AXIS));
        line11.setUIID("textfieldLarge");
        TableLayout tlvii = new TableLayout(1, 2);
        e6.add(sl11);
        Container c11 = new Container(tliv);
        c11.add(tlvii.createConstraint().widthPercentage(40), e6).
                add(tlvii.createConstraint().widthPercentage(60).verticalAlign(Component.CENTER), line11);
        resp.add(c11);
        return resp;
    }

which builds the attached screenshot:

This is the first instance that a layout I have used has left gaps between containers. Besides not needing the button to run the exercise in the Replay Screen, I do not see any difference between Exercise 3 and 4, and Exercises 4 and 5, then repeating between 5 and 6. Anyone have any ideas?

The gap is probably due to margin between components e.g. textMedium might have some margin defined which would cause that spacing.

Open the component inspector and point at the component in the tree which would highlight it in red. You can then see which component occupies the space in the gap. Then you can see the UIID it has and inspect that UIID in CSS to see what triggered the problem.