CheckboxTableViewer won't show the label of checkboxes

In Java, I am using CheckboxTableViewer to display a checklist for the user. I am populating the checklist using setInput method, as shown below. But for some reason, when I run my code, which resides in a Wizard Page, it shows the checkboxes but not the labels of the boxes (no text at all, as if I am passing empty strings). How can I fix the problem? Thank You. Below is my code

public void createControl(Composite arg0) {

        Composite container = new Composite(arg0, SWT.NONE);
        container.setLayout(new GridLayout());

        GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, true);
        container.setLayoutData(layoutData);

        checkboxTableViewer = CheckboxTableViewer.newCheckList(container,
                SWT.FULL_SELECTION | SWT.BORDER);
        checkboxTableViewer.getTable().setLinesVisible(true);
        checkboxTableViewer.getTable().setSize(500, 500);
        checkboxTableViewer.setContentProvider(new ArrayContentProvider());
        checkboxTableViewer.setLabelProvider(new ITableLabelProvider() {

            public void removeListener(ILabelProviderListener listener) {
                // TODO Auto-generated method stub

            }

            public Image getColumnImage(Object element, int columnIndex) {
                // TODO Auto-generated method stub
                return null;
            }

            public String getColumnText(Object element, int columnIndex) {
                // TODO Auto-generated method stub
                return null;
            }

            public void addListener(ILabelProviderListener listener) {
                // TODO Auto-generated method stub

            }

            public void dispose() {
                // TODO Auto-generated method stub

            }

            public boolean isLabelProperty(Object element, String property) {
                // TODO Auto-generated method stub
                return false;
            }
        });

        checkboxTableViewer.setInput(new String[]{"zaid","saad","ahmad"});

        checkboxTableViewer.addCheckStateListener(new ICheckStateListener() {

            public void checkStateChanged(CheckStateChangedEvent event) {
                if (checkboxTableViewer.getCheckedElements().length > 0) {
                    enableNext = true;
                } else {
                    enableNext = false;
                }
                checkStatus();

            }

            private void checkStatus() {
                canFlipToNextPage();
                // explicit call
                getWizard().getContainer().updateButtons();

            }
        });

        setControl(container);

    }