分割圧縮ファイルの解凍

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

public class FileProcessor {

public static void main(String[] args) {
    splitAndCombineFiles("/input/sample.docx", "/split", "/output/sample.docx");
}

private static void splitAndCombineFiles(String inputPath, String splitFolderPath, String outputPath) {
    try {
        // Split the original file
        splitFile(inputPath, splitFolderPath);

        // Combine the split files
        combineFiles(splitFolderPath, outputPath);

    } catch (IOException e) {
        e.printStackTrace();
    }
}

private static void splitFile(String inputPath, String splitFolderPath) throws IOException {
    File inputFile = new File(inputPath);
    byte[] fileContent = readBytesFromFile(inputFile);

    int sections = 3;
    int bytesPerSection = fileContent.length / sections;

    for (int i = 0; i < sections; i++) {
        int startIndex = i * bytesPerSection;
        int endIndex = (i == sections - 1) ? fileContent.length : (i + 1) * bytesPerSection;

        byte[] sectionContent = new byte[endIndex - startIndex];
        System.arraycopy(fileContent, startIndex, sectionContent, 0, sectionContent.length);

        writeBytesToFile(splitFolderPath + "/split" + (i + 1) + ".bin", sectionContent);
    }
}

private static void combineFiles(String splitFolderPath, String outputPath) throws IOException {
    List<byte[]> splitContents = new ArrayList<>();

    // Load split files
    for (int i = 1; i <= 3; i++) {
        byte[] content = readBytesFromFile(new File(splitFolderPath + "/split" + i + ".bin"));
        splitContents.add(content);
    }

    // Combine split contents
    byte[] combinedContent = concatenateByteArrays(splitContents);

    // Save combined content to output file
    writeBytesToFile(outputPath, combinedContent);
}

private static byte[] readBytesFromFile(File file) throws IOException {
    try (FileInputStream fis = new FileInputStream(file);
         ByteArrayOutputStream bos = new ByteArrayOutputStream()) {

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = fis.read(buffer)) != -1) {
            bos.write(buffer, 0, bytesRead);
        }

        return bos.toByteArray();
    }
}

private static void writeBytesToFile(String filePath, byte[] content) throws IOException {
    try (FileOutputStream fos = new FileOutputStream(filePath)) {
        fos.write(content);
    }
}

private static byte[] concatenateByteArrays(List<byte[]> byteArrays) {
    int totalLength = 0;
    for (byte[] array : byteArrays) {
        totalLength += array.length;
    }

    byte[] result = new byte[totalLength];
    int currentIndex = 0;

    for (byte[] array : byteArrays) {
        System.arraycopy(array, 0, result, currentIndex, array.length);
        currentIndex += array.length;
    }

    return result;
}

}