java 文件操作工具

ゝ一纸荒年。 2023-10-15 10:13 116阅读 0赞

#### 文章目录 ####

*   *  1、文件切片
     *   *  1.1、File 切片成 N 个保存到本地
         *  1.2、MultipartFile 切成 N 个 InputStream
     *  2、目录中的文件读取

### 1、文件切片 ###

#### 1.1、File 切片成 N 个保存到本地 ####

/**
         * 读取本地文件 sourceFile ， 切成 chunkSize 个文件
         * @param sourceFile 源文件
         * @param splitFilePath 切片后要保存的目录
         * @param chunkSize 切片数量
         */
        public static void fileChunking(String sourceFile, String splitFilePath, int chunkSize) {
        
            try (FileInputStream fis = new FileInputStream(sourceFile)) {
        
                byte[] buffer = new byte[chunkSize];
                int bytesRead;
                int chunkNumber = 1;
    
                while ((bytesRead = fis.read(buffer)) > 0) {
        
                    String chunkFileName = splitFilePath + "chunking" + chunkNumber + ".txt";
                    try (FileOutputStream fos = new FileOutputStream(chunkFileName)) {
        
                        fos.write(buffer, 0, bytesRead);
                    }
                    chunkNumber++;
                }
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }

使用示例

fileChunking("D:\\1.txt", "D:\\chunking", 3);

#### 1.2、MultipartFile 切成 N 个 InputStream ####

将 前端输入进来的文件 分成N个输入流

/**
         * 将 前端输入进来的文件 分成N个输入流
         * @param file 前端输入进来的文件
         * @return 输出流List
         */
        public static List<InputStream> splitFile(MultipartFile file) {
        
            try {
        
                int chunkSize = 3; // 每个分片的大小，这里设置为1MB，可以根据需要进行调整
                byte[] fileBytes =  file.getBytes();
                int totalChunks = (int) Math.ceil((double) fileBytes.length / chunkSize);
                List<InputStream> chunkInputStreams = new ArrayList<>();
    
                for (int i = 0; i < totalChunks; i++) {
        
                    int offset = i * chunkSize;
                    int chunkLength = Math.min(chunkSize, fileBytes.length - offset);
                    byte[] chunkBytes = new byte[chunkLength];
                    System.arraycopy(fileBytes, offset, chunkBytes, 0, chunkLength);
                    InputStream chunkInputStream = new ByteArrayInputStream(chunkBytes);
                    chunkInputStreams.add(chunkInputStream);
                }
                return chunkInputStreams;
            } catch (IOException e) {
        
                throw new RuntimeException(e);
            }
        }
    
    // 使用示例：List<InputStream> inputStreams = splitFile(file);

将输出流Lits保存为多个文件

/**
         * 将多个输出流保存为多个文件
         * @param inputStreams 输出流List
         * @param outputDirectory 要保存文件的目录
         */
        public static void saveToMultipleFiles(List<InputStream> inputStreams, String outputDirectory) {
        
            File directory = new File(outputDirectory);
            if (!directory.exists()) {
        
                directory.mkdirs();
            }
    
            try {
        
                for (int i = 0; i < inputStreams.size(); i++) {
        
                    String filePath = outputDirectory + File.separator + "file" + (i + 1) + ".txt";
                    try (BufferedOutputStream outputStream = new BufferedOutputStream(new FileOutputStream(filePath))) {
        
                        InputStream inputStream = inputStreams.get(i);
                        byte[] buffer = new byte[1024];
                        int bytesRead;
                        while ((bytesRead = inputStream.read(buffer)) != -1) {
        
                            outputStream.write(buffer, 0, bytesRead);
                        }
                    }
                }
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }
    
    // 使用示例： saveToMultipleFiles(inputStreams, "D:\\test\\");

### 2、目录中的文件读取 ###

读取一个目录下所有txt后缀的文件，按文件内容输出为List<List>

import java.io.BufferedReader;
    import java.io.FileReader;
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.stream.Collectors;
    
    public class FileProcessor {
        
        public static void main(String[] args) throws IOException {
        
            String directoryPath = "/path/to/directory"; // 替换为实际的目录路径
    
            List<List<String>> fileContents = readTxtFiles(directoryPath);
            fileContents.forEach(System.out::println);
        }
    
        public static List<List<String>> readTxtFiles(String directoryPath) throws IOException {
        
            List<Path> txtFiles = Files.walk(Paths.get(directoryPath))
                    .filter(Files::isRegularFile)
                    .filter(path -> path.toString().endsWith(".txt"))
                    .collect(Collectors.toList());
    
            List<List<String>> fileContents = new ArrayList<>();
    
            for (Path txtFile : txtFiles) {
        
                List<String> lines = new ArrayList<>();
    
                try (BufferedReader reader = new BufferedReader(new FileReader(txtFile.toFile()))) {
        
                    String line;
                    while ((line = reader.readLine()) != null) {
        
                        lines.add(line);
                    }
                }
    
                fileContents.add(lines);
            }
    
            return fileContents;
        }
    }