final ExecutorService executorService = Executors.newFixedThreadPool(options.numOfThreads);
        try {
            while (count != 0) {
                count = ComponentUtil.getThumbnailManager().generate(executorService, options.cleanup);
                totalCount += count;
            }
            executorService.shutdown();
            executorService.awaitTermination(60, TimeUnit.SECONDS);

package org.codelibs.fess.thumbnail;

import java.io.File;
import java.util.Map;

import org.codelibs.core.misc.Tuple3;

public interface ThumbnailGenerator {

    String getName();

    boolean generate(String thumbnailId, File outputFile);

    boolean isTarget(Map<String, Object> docMap);

    boolean isAvailable();

    void destroy();