Bug 221649 [Import/Export] ZipFileImportWizard has no option to change the FILE_IMPORT_MASK
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardArchiveFileResourceImportPage1.java
*	and is valid (ie.- proper format)
     */
    protected boolean ensureSourceIsValid() {
    	if (ArchiveFileManipulations.isTarFile(sourceNameField.getText())) {
    		return ensureTarSourceIsValid();
    	}
    	return ensureZipSourceIsValid();
    }
    
    /**
     * The Finish button was pressed.  Try to do the required work now and answer
     * a boolean indicating success.  If <code>false</code> is returned then the
     * wizard will not close.
     *
     * @return boolean
     */
    public boolean finish() {
        if (!super.finish()) {
			return false;
		}
        disposeStructureProvider();
		return true;
	}
    /**
     * Closes the structure provider and sets
     * the field to <code>null</code>.
     * 
     * @since 3.4
     */
	private void disposeStructureProvider() {