* Uses external tools through command execution to generate thumbnail images from documents.
 */
public class CommandGenerator extends BaseThumbnailGenerator {
    private static final Logger logger = LogManager.getLogger(CommandGenerator.class);

    /** List of command strings to execute for thumbnail generation. */
    protected List<String> commandList;

            }
        }
    }

    // Test concurrent access patterns
    public void test_concurrent_operations() throws Exception {
        final CommandGenerator generator1 = new CommandGenerator();
        final CommandGenerator generator2 = new CommandGenerator();

        generator1.setCommandList(Collections.singletonList("echo test1"));
        generator2.setCommandList(Collections.singletonList("echo test2"));