面试题：Java模板方法模式在批量数据处理中如何优化性能

多线程处理优化

思路：将批量数据划分成多个子任务，利用多线程并行处理这些子任务，从而加快整体处理速度。
关键代码片段：

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

// 定义任务类
class BatchTask implements Callable<List<Result>> {
    private List<Data> subDataList;
    // 假设Data和Result是自定义的数据和结果类型

    public BatchTask(List<Data> subDataList) {
        this.subDataList = subDataList;
    }

    @Override
    public List<Result> call() throws Exception {
        List<Result> results = new ArrayList<>();
        for (Data data : subDataList) {
            // 具体处理逻辑，这里假设存在process方法
            Result result = process(data);
            results.add(result);
        }
        return results;
    }

    private Result process(Data data) {
        // 实际处理数据的方法
        return new Result();
    }
}

// 模板方法类
abstract class BatchDataProcessor {
    public final List<Result> processBatchData(List<Data> dataList) {
        int numThreads = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numThreads);
        List<Future<List<Result>>> futures = new ArrayList<>();
        int subListSize = dataList.size() / numThreads;

        for (int i = 0; i < numThreads; i++) {
            int fromIndex = i * subListSize;
            int toIndex = (i == numThreads - 1)? dataList.size() : (i + 1) * subListSize;
            List<Data> subDataList = dataList.subList(fromIndex, toIndex);
            BatchTask task = new BatchTask(subDataList);
            futures.add(executorService.submit(task));
        }

        List<Result> allResults = new ArrayList<>();
        for (Future<List<Result>> future : futures) {
            try {
                allResults.addAll(future.get());
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            }
        }

        executorService.shutdown();
        return allResults;
    }
}

资源复用优化

思路：避免在每次处理数据时重复创建相同的资源，如数据库连接、网络连接等，而是复用已创建的资源。
关键代码片段：

// 资源管理类，单例模式保证资源唯一
class ResourceManager {
    private static ResourceManager instance;
    private Connection connection; // 假设是数据库连接

    private ResourceManager() {
        // 初始化资源
        connection = DriverManager.getConnection("url", "user", "password");
    }

    public static ResourceManager getInstance() {
        if (instance == null) {
            synchronized (ResourceManager.class) {
                if (instance == null) {
                    instance = new ResourceManager();
                }
            }
        }
        return instance;
    }

    public Connection getConnection() {
        return connection;
    }
}

// 模板方法类修改，复用资源
abstract class BatchDataProcessorWithResourceReuse {
    public final List<Result> processBatchData(List<Data> dataList) {
        ResourceManager resourceManager = ResourceManager.getInstance();
        Connection connection = resourceManager.getConnection();
        List<Result> results = new ArrayList<>();
        for (Data data : dataList) {
            // 使用复用的连接处理数据
            Result result = process(data, connection);
            results.add(result);
        }
        return results;
    }

    abstract Result process(Data data, Connection connection);
}

星途面试题库

面试题：Java模板方法模式在批量数据处理中如何优化性能

知识考点

面试题答案

多线程处理优化

资源复用优化