Channel | Buffer 完成文件複製

1、使用直接緩衝區完成文件的複製 ( 內存映射文件 )

---

JDK 1.7 後 提供

上面的 create 的話就是:
不存在就建立
存在的話就覆蓋..

/**  
   *  2. 使用 直接緩衝區 完成文件的複製 (內存映射文件) 
   *   直接緩衝區 -->  只有 byte 支持 
   */
@Test  
public void test2(){  
  
    FileChannel inChannel = null;  
  FileChannel outChannle = null;  
  
 try {  
        inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);  
  
  outChannle = FileChannel.open(Paths.get("3.jpg"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE\_NEW);  
  
  // 這個就是 內存映射文件  
  MappedByteBuffer inMappedBuf = inChannel.map(FileChannel.MapMode.READ\_ONLY, 0 , inChannel.size());  
  MappedByteBuffer outMappedBuf = outChannle.map(FileChannel.MapMode.READ\_WRITE, 0, inChannel.size());  
  // 上面的兩個內存映射文件都在 物理內存中....  
  
  
 // 如今的優勢, 只須要從緩衝區中讀寫操做..  
 byte[] dst = new byte[inMappedBuf.limit()];  
  
  inMappedBuf.get(dst);  
  outMappedBuf.put(dst);  
  
  } catch (IOException e) {  
        e.printStackTrace();  
  } finally {  
        if(inChannel != null){  
            try {  
                inChannel.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
        if(outChannle != null){  
            try {  
                outChannle.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
    }  
  
}

2、 利用通道完成文件的複製 (非直接緩衝區的)

---

/\*\*  
 \*    1. 利用通道完成文件的複製  (非直接緩衝區的) \*/@Test  
public void test1(){  
  
    FileInputStream fis = null;  
  FileOutputStream fos = null;  
  FileChannel inChannel = null;  
  FileChannel outChannel = null;  
  
 try {  
        fis = new FileInputStream("1.jpg");  
  fos = new FileOutputStream("2.jpg");  
  
  // 1. 獲取通道  
  inChannel = fis.getChannel();  
  outChannel = fos.getChannel();  
  
  // 2. 分配指定大小的緩衝區.  
  ByteBuffer buf = ByteBuffer.allocate(1024);  
  
  
  // 3. 讀取數據  
 // 將 通道中的數據存入緩衝區中  while(inChannel.read(buf) != -1){  
            // 切換成讀取數據模式  
  buf.flip();  
  
  // 4. 寫入數據  
 // 將緩存區的數據寫入到 通道中  outChannel.write(buf);  
  
  // 清空緩衝區  
  buf.clear();  
  }  
  
  
    } catch (IOException e) {  
        e.printStackTrace();  
  } finally {  
        if(outChannel != null){  
            try {  
                outChannel.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
        if(inChannel != null){  
            try {  
                inChannel.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
        if(fos != null){  
            try {  
                fos.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
        if(fis != null){  
            try {  
                fis.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
    }  
  
}

3、通道之間的數據傳輸

---

/\*\*  
 \*  通道之間的數據傳輸 \*/@Test  
public void test3(){  
    FileChannel inChannel = null;  
  FileChannel outChannle = null;  
  
 try {  
        inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);  
  
  outChannle = FileChannel.open(Paths.get("4.jpg"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE\_NEW);  
  
  inChannel.transferTo(0, inChannel.size(), outChannle);  
  
  // 這個 outChannel 也行...  
 //   outChannle.transferFrom(inChannel, 0, inChannel.size());  
  }catch (IOException e){  
        e.printStackTrace();  
  } finally {  
        if(inChannel != null){  
            try {  
                inChannel.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
  
        if(outChannle != null){  
            try {  
                outChannle.close();  
  } catch (IOException e) {  
                e.printStackTrace();  
  }  
        }  
    }  
  
}