UF.IMAGEIO

当尝试使用已被释放的资源时，就会报告 UF（使用已释放）问题。UF.IMAGEIO 警告表明尝试在 ImageIO 流已被关闭后使用它。

示例 1

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     public boolean canDecodeInput(ImageInputStream stream) {
         byte[] b = new byte[8];
         try {
             final long l = stream.length();
             if (l > 655335) {
                 return false;
             }
             stream.mark();
             stream.readFully(b);
             stream.reset();
         } catch (IOException e) {
             return false;
         } finally {
             try {
                 stream.close();
             } catch (IOException e) {
                 // do nothing
             }
         }
 
         // Cast unsigned character constants prior to comparison
         return (b[0] == (byte) 'm' && b[1] == (byte) 'y' &&
                 b[2] == (byte) 'f' && b[3] == (byte) 'o' &&
                 b[4] == (byte) 'r' && b[5] == (byte) 'm' &&
                 b[6] == (byte) 'a' && b[7] == (byte) 't');
     }
 
     public void decode(Object data) throws IOException {
         final ImageInputStream stream = ImageIO.createImageInputStream(data);
         if (canDecodeInput(stream)) {
             try {
                 final int[] colors = new int[(int) stream.length()];
                 for (int i = 0; i < colors.length; i++) {
                     colors[i] = stream.readInt();
                 }
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
 
     }

针对第 48 行的代码段报告 UF.IMAGEIO：在第 31 行关闭了图像输入流 stream 后再次使用它。

示例 2

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     public boolean canDecodeInput(ImageInputStream stream) {
         byte[] b = new byte[8];
         try {
             final long l = stream.length();
             if (l > 655335) {
                 return false;
             }
             stream.mark();
             stream.readFully(b);
             stream.reset();
         } catch (IOException e) {
             return false;
         }
 
         // Cast unsigned character constants prior to comparison
         return (b[0] == (byte) 'm' && b[1] == (byte) 'y' &&
                 b[2] == (byte) 'f' && b[3] == (byte) 'o' &&
                 b[4] == (byte) 'r' && b[5] == (byte) 'm' &&
                 b[6] == (byte) 'a' && b[7] == (byte) 't');
     }
 
     public void decode(Object data) throws IOException {
         final ImageInputStream stream = ImageIO.createImageInputStream(data);
         try {
             if (canDecodeInput(stream)) {
                 try {
                     final int[] colors = new int[(int) stream.length()];
                     for (int i = 0; i < colors.length; i++) {
                         colors[i] = stream.readInt();
                     }
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
         } finally {
             stream.close();
         }
     }

来自之前部分的代码段经过了修复。方法“canDecodeInput”不再关闭流。现在，它通过“decode”方法来关闭，即开启该流的方法。通常，通过最初用来分配资源的相同方法来释放资源是良好的编码做法。