Java中如何在main方法调用OutputCountsAsCSV并传递统计结果

我尝试加载JSON文件并转换为ConcurrentHashMap，再将词频统计结果写入CSV文件，编写了DescriptiveStatistics类代码。现在需要在main(String[] args)方法中调用OutputCountsAsCSV方法，传入CountWordsInCorpus返回的词频统计ConcurrentHashMap和文件名'my_file.csv'，但调用时出现参数不匹配错误，请问该如何正确实现？

JSON文件格式示例 #

{"lemmas":{"doc4":"which might make it go wrong","doc3":"and no dirty datum","doc2":"each of vary length","doc1":"you should find that it have five line","doc0":"this be a simple text file"}}

原实现代码 #

package pipeline;

import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;

import helpers.JSONIOHelper;

public class DescriptiveStatistics {

    private static void StartCreatingStatistics(String filePath) {
        System.out.println("Loading file...");

        JSONIOHelper JSONIO = new JSONIOHelper();
        JSONIO.LoadJSON(filePath);
        ConcurrentHashMap<String, String> lemmas = JSONIO.GetLemmasFromJSONStructure();
        
        lemmas.forEach((k, v) -> System.out.printf("    %s%n", v));

        CountWordsInCorpus(lemmas);
    }

    private static ConcurrentHashMap<String, Integer> CountWordsInCorpus(ConcurrentHashMap<String, String> lemmas) {
        ArrayList<String> corpus = new ArrayList<String>();
        ConcurrentHashMap<String, Integer> counts = new ConcurrentHashMap<String, Integer>();
    
        for (Entry<String, String> entry : lemmas.entrySet()) {
            for (String word : entry.getValue().split(" ")) {
                corpus.add(word);
            }
        }

        for (String word : corpus) {
            if (counts.containsKey(word)) {
                counts.put(word, counts.get(word) + 1);
            } else {
                counts.put(word, 1);
            }
        }
        return counts;
    }

    private void OutputCountsAsCSV(ConcurrentHashMap<String, Integer> counts, String filename) {
        String CSVOutput = new String("");

        for (Entry<String, Integer> entry : counts.entrySet()) {
            String rowText = String.format("%s,%d\n", entry.getKey(), entry.getValue());
            System.out.println(rowText);
            CSVOutput += rowText;
            System.out.println(CSVOutput);

            try (FileWriter writer = new FileWriter(filename)) {
                writer.write(CSVOutput);
                System.out.println("CSV File saved successfully...");
            } catch (Exception e) {
                System.out.println("Saving CSV to file failed...");
            }
        }
    }
}

错误的main方法尝试 #

public static void main(String[] args) {
    String filePath = "JSON_simple.json";
    DescriptiveStatistics newobj = new DescriptiveStatistics();
    newobj.StartCreatingStatistics(filePath);
    String filename = "my_file.csv";
    // 尝试获取CountWordsInCorpus返回值时出现参数不匹配错误
    // ConcurrentHashMap<String, Integer> newhashmap = newobj.CountWordsInCorpus()
    OutputCountsAsCSV(newhashmap, filename);
}

问题分析与修复方案 #

1. 静态方法与实例方法调用混淆 #

• CountWordsInCorpus是静态方法，不能通过实例对象newobj调用，直接用类名调用即可；同时它需要传入ConcurrentHashMap<String, String>类型的参数。
• OutputCountsAsCSV是实例方法，必须通过类的实例对象调用，或者改为静态方法以便在main中直接调用。

2. 方法参数缺失 #

原main方法中调用CountWordsInCorpus时没有传入必要的lemmas参数，导致参数不匹配错误。

3. CSV写入逻辑优化 #

原OutputCountsAsCSV方法在循环内重复打开/关闭文件，会导致文件被多次覆盖且效率低下，应该将文件写入操作放在循环外部。

修复后的完整代码 #

调整后的DescriptiveStatistics类 #

package pipeline;

import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;

import helpers.JSONIOHelper;

public class DescriptiveStatistics {

    // 修改方法，返回统计结果以便后续使用
    private static ConcurrentHashMap<String, Integer> StartCreatingStatistics(String filePath) {
        System.out.println("Loading file...");

        JSONIOHelper JSONIO = new JSONIOHelper();
        JSONIO.LoadJSON(filePath);
        ConcurrentHashMap<String, String> lemmas = JSONIO.GetLemmasFromJSONStructure();
        
        lemmas.forEach((k, v) -> System.out.printf("    %s%n", v));

        // 直接返回统计结果
        return CountWordsInCorpus(lemmas);
    }

    private static ConcurrentHashMap<String, Integer> CountWordsInCorpus(ConcurrentHashMap<String, String> lemmas) {
        ArrayList<String> corpus = new ArrayList<String>();
        ConcurrentHashMap<String, Integer> counts = new ConcurrentHashMap<String, Integer>();
    
        for (Entry<String, String> entry : lemmas.entrySet()) {
            for (String word : entry.getValue().split(" ")) {
                corpus.add(word);
            }
        }

        // 简化计数逻辑
        for (String word : corpus) {
            counts.put(word, counts.getOrDefault(word, 0) + 1);
        }
        return counts;
    }

    // 修改为静态方法，方便在main中直接调用
    private static void OutputCountsAsCSV(ConcurrentHashMap<String, Integer> counts, String filename) {
        StringBuilder CSVOutput = new StringBuilder(); // 用StringBuilder提升字符串拼接效率

        // 先拼接所有行数据
        for (Entry<String, Integer> entry : counts.entrySet()) {
            String rowText = String.format("%s,%d%n", entry.getKey(), entry.getValue());
            System.out.println(rowText);
            CSVOutput.append(rowText);
        }

        // 一次性写入文件
        try (FileWriter writer = new FileWriter(filename)) {
            writer.write(CSVOutput.toString());
            System.out.println("CSV File saved successfully...");
        } catch (Exception e) {
            System.out.println("Saving CSV to file failed...");
            e.printStackTrace(); // 打印异常信息便于排查问题
        }
    }

    // 正确的main方法
    public static void main(String[] args) {
        String filePath = "JSON_simple.json";
        // 获取词频统计结果
        ConcurrentHashMap<String, Integer> wordCounts = StartCreatingStatistics(filePath);
        String filename = "my_file.csv";
        // 调用静态方法写入CSV
        OutputCountsAsCSV(wordCounts, filename);
    }
}

内容的提问来源于stack exchange，提问作者Bluetail