java實現檔案拷貝的七種方式

阿新 • • 發佈：2020-02-05

1. 通過位元組流實現檔案的拷貝

 /**
   * 通過位元組流實現檔案的拷貝
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByStream(String sourcePath,String targetPath){
    //原始檔路徑
    File source = new File(sourcePath);
    //目標檔案路徑
    File target = new File(targetPath);

    //如果原始檔不存在則不能拷貝
    if(!source.exists()){
      return;
    }
    //如果目標檔案目錄不存在則建立
    if(!target.getParentFile().exists()){
      target.getParentFile().mkdirs();
    }

    try {
      //實現檔案的拷貝
      InputStream inputStream = new FileInputStream(source);
      OutputStream outputStream = new FileOutputStream(target);
      int temp = 0;
      //每次讀取1024個位元組
      byte[] data = new byte[1024];
      //將每次讀取的資料儲存到位元組數組裡面，並且返回讀取的個數
      while ((temp = inputStream.read(data)) != -1){
        //輸出陣列
        outputStream.write(data,temp);
      }

      inputStream.close();
      outputStream.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

2. 通過字元流實現檔案拷貝

使用字元流只能拷貝文字檔案

  /**
   * 通過字元流實現檔案的拷貝
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByReaderAndWriter(String sourcePath,String targetPath) {
    //原始檔路徑
    File source = new File(sourcePath);
    //目標檔案路徑
    File target = new File(targetPath);

    //如果原始檔不存在則不能拷貝
    if (!source.exists()) {
      return;
    }
    //如果目標檔案目錄不存在則建立
    if (!target.getParentFile().exists()) {
      target.getParentFile().mkdirs();
    }

    FileReader in = null;
    FileWriter out = null;
    try {
      //字元輸入流和字元輸出流
      in = new FileReader(source);
      out = new FileWriter(target);

      char[] c = new char[1024];
      int temp = 0;
      //每次讀取1024個字元
      while ((temp = in.read(c)) != -1) {
        //輸出到檔案
        out.write(c,temp);
      }
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      //關閉流
      try {
        if (in != null) {
          in.close();
        }
        if (out != null) {
          out.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

3. 通過位元組緩衝流實現檔案拷貝

/**
   * 通過位元組緩衝流實現檔案的拷貝
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByBuffered(String sourcePath,String targetPath){
    //原始檔路徑
    File source = new File(sourcePath);
    //目標檔案路徑
    File target = new File(targetPath);

    //如果原始檔不存在則不能拷貝
    if (!source.exists()) {
      return;
    }
    //如果目標檔案目錄不存在則建立
    if (!target.getParentFile().exists()) {
      target.getParentFile().mkdirs();
    }

    InputStream in = null;
    OutputStream out = null;
    try {
      //位元組緩衝輸入流和位元組緩衝輸出流
      in = new BufferedInputStream(new FileInputStream(source));
      out = new BufferedOutputStream(new FileOutputStream(target));

      byte[] b = new byte[1024];
      int temp = 0;
      //每次讀取一個1024的位元組陣列
      while((temp = in.read(b)) != -1){
        //輸出到檔案
        out.write(b,temp);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }finally {
      //關閉流
      try {
        if (in != null) {
          in.close();
        }
        if (out != null) {
          out.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

4. 通過字元緩衝流拷貝檔案

字元緩衝流只能讀取文字檔案

 /**
   * 通過字元緩衝流實現檔案的拷貝
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByBufferedChar(String sourcePath,String targetPath){
    //原始檔路徑
    File source = new File(sourcePath);
    //目標檔案路徑
    File target = new File(targetPath);

    //如果原始檔不存在則不能拷貝
    if (!source.exists()) {
      return;
    }
    //如果目標檔案目錄不存在則建立
    if (!target.getParentFile().exists()) {
      target.getParentFile().mkdirs();
    }

    BufferedReader in = null;
    BufferedWriter out = null;

    try {
      //字元緩衝輸入流和字元緩衝輸出流
      in = new BufferedReader(new FileReader(source));
      out = new BufferedWriter(new FileWriter(target));

      //讀取檔案（每次讀取一行）
      String temp = null;
      while((temp = in.readLine()) != null){
        //輸出到檔案
        out.write(temp);
      }

    } catch (Exception e) {
      e.printStackTrace();
    }finally {
      //關閉流
      try {
        if (in != null) {
          in.close();
        }
        if (out != null) {
          out.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

5. 通過JAVA NIO 非直接緩衝區拷貝檔案

  /**
   * 通過JAVA NIO 非直接緩衝區拷貝檔案
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByChannel(String sourcePath,String targetPath) {
    FileChannel outChannel = null;
    FileChannel inChannel = null;

    FileInputStream fis = null;
    FileOutputStream fos = null;

    try {
      fis = new FileInputStream(sourcePath);
      fos = new FileOutputStream(targetPath);

      //獲取通道
      inChannel = fis.getChannel();
      outChannel = fos.getChannel();

      //分配指定大小的緩衝區
      ByteBuffer buf = ByteBuffer.allocate(1024);

      while (inChannel.read(buf) != -1) {
        //轉換為讀取資料模式
        buf.flip();
        //寫入到磁碟
        outChannel.write(buf);
        //清空緩衝區
        buf.clear();
      }

    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      //關閉流
      try {
        if (outChannel != null) {
          outChannel.close();
        }
        if (inChannel != null) {
          inChannel.close();
        }
        if (fis != null) {
          fis.close();
        }
        if (fos != null) {
          fos.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

6. 通過JAVA NIO 直接緩衝區拷貝檔案

/**
   * 通過JAVA NIO 直接緩衝區拷貝檔案（記憶體對映檔案）
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByChannelBufferd(String sourcePath,String targetPath) {
    FileChannel inChannel = null;
    FileChannel outChannel = null;
    try {
      //獲取通道,StandardOpenOption.READ表示可讀，StandardOpenOption.WRITE表示可寫，StandardOpenOption.CREATE表示可以建立
      inChannel = FileChannel.open(Paths.get(sourcePath),StandardOpenOption.READ);
      outChannel = FileChannel.open(Paths.get(targetPath),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE);

      //建立記憶體對映檔案
      MappedByteBuffer inMapped = inChannel.map(FileChannel.MapMode.READ_ONLY,inChannel.size());
      MappedByteBuffer outMapped = outChannel.map(FileChannel.MapMode.READ_WRITE,inChannel.size());

      //直接操作記憶體對映檔案
      byte[] buf = new byte[inMapped.limit()];
      inMapped.get(buf);
      outMapped.put(buf);

    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      //關閉流
      try {
        if (outChannel != null) {
          outChannel.close();
        }
        if (inChannel != null) {
          inChannel.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

7. 通過JAVA NIO 通道傳輸拷貝檔案

方式一

 /**
   * 通過JAVA NIO 通道傳輸拷貝檔案
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByChannelTransfer(String sourcePath,String targetPath) {
    FileChannel inChannel = null;
    FileChannel outChannel = null;
    try {
      //獲取通道
      inChannel = FileChannel.open(Paths.get(sourcePath),StandardOpenOption.CREATE);

      inChannel.transferTo(0,inChannel.size(),outChannel);
    } catch (IOException e) {
      e.printStackTrace();
    }finally {
      //關閉流
      try {
        if (outChannel != null) {
          outChannel.close();
        }
        if (inChannel != null) {
          inChannel.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

方式二

 /**
   * 通過JAVA NIO 通道傳輸拷貝檔案
   *
   * @param sourcePath 原始檔路徑
   * @param targetPath 目標檔案路徑
   */
  public static void copyFileByChannelTransfer2(String sourcePath,String targetPath) {
    FileInputStream fis = null;
    FileOutputStream fos = null;
    FileChannel inChannel = null;
    FileChannel outChannel = null;
    try {
      fis = new FileInputStream(sourcePath);
      fos = new FileOutputStream(targetPath);

      //獲取通道
      inChannel = fis.getChannel();
      outChannel = fos.getChannel();

      inChannel.transferTo(0,outChannel);
    } catch (IOException e) {
      e.printStackTrace();
    }finally {
      //關閉流
      try {
        if (outChannel != null) {
          outChannel.close();
        }
        if (inChannel != null) {
          inChannel.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

使用示例

    String source = "e:\\demo\\縱天神帝.txt";
    String target = "e:\\demo\\";
    long time1 = System.currentTimeMillis();
    copyFileByStream(source,target + "1.txt");
    System.out.println("通過位元組流實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time1));

    long time2 = System.currentTimeMillis();
    copyFileByReaderAndWriter(source,target + "2.txt");
    System.out.println("通過字元流實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time2));

    long time3 = System.currentTimeMillis();
    copyFileByBuffered(source,target + "3.txt");
    System.out.println("通過位元組緩衝流實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time3));

    long time4 = System.currentTimeMillis();
    copyFileByBufferedChar(source,target + "4.txt");
    System.out.println("通過字元緩衝流實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time4));

    long time5 = System.currentTimeMillis();
    copyFileByChannel(source,target + "5.txt");
    System.out.println("通過JAVA NIO通道（非直接緩衝區）實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time5));

    long time6 = System.currentTimeMillis();
    copyFileByChannelBufferd(source,target + "6.txt");
    System.out.println("通過JAVA NIO通道（直接緩衝區）實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time6));

    long time7 = System.currentTimeMillis();
    copyFileByChannelTransfer(source,target + "7.txt");
    System.out.println("通過JAVA NIO通道傳輸實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time7));

    long time8 = System.currentTimeMillis();
    copyFileByChannelTransfer(source,target + "8.txt");
    System.out.println("通過JAVA NIO通道傳輸2實現檔案的拷貝耗時：" + (System.currentTimeMillis() - time8));

通過測試發現，使用JAVA NIO通道傳輸、JAVA NIO通道直接緩衝區以及位元組緩衝流拷貝檔案效率最高

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