package wenjianyuliu;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

//編寫一個檔案分割工具，能把一個大檔案分割成多個小的檔案。並且能再次把它們合併起來得到完整的檔案
public class CutFile {
    public static void main(String[] args) {
        //呼叫cutFile()函式 傳人蔘數分別為 （原大檔案，切割後存放的小檔案的路徑，切割規定的記憶體大小）
        cutFile("E:\\新建資料夾\\poem2.txt", "E:\\80747",1024 * 1024 * 20);
    }

    private static void cutFile(String src, String endsrc, int num) {
        FileInputStream fis = null;
        File file = null;
        try {
            fis = new FileInputStream(src);
            file = new File(src);
            //建立規定大小的byte陣列
            byte[] b = new byte[num];
            int len = 0;
            //name為以後的小檔案命名做準備
            int name = 1;
            //遍歷將大檔案讀入byte陣列中，當byte陣列讀滿後寫入對應的小檔案中
            while ((len = fis.read(b)) != -1) {
                //分別找到原大檔案的檔名和檔案型別，為下面的小檔案命名做準備
                String name2 = file.getName();
                int lastIndexOf = name2.lastIndexOf(".");
                String substring = name2.substring(0, lastIndexOf);
                String substring2 = name2.substring(lastIndexOf, name2.length());
                FileOutputStream fos = new FileOutputStream(endsrc + "\\\\"+ substring + "-" + name + substring2);
                //將byte陣列寫入對應的小檔案中
                fos.write(b, 0, len);
                //結束資源
                fos.close();
                name++;
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fis != null) {
                    //結束資源
                    fis.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}