从阅读器中删除或忽略字符

Question

我正在将所有字符读入流中。我正在使用 inputStream.read 阅读它。这是 java.io.Reader 输入流。 读入缓冲区时如何忽略 @ 等特殊字符。

代码

private final void FillBuff() throws java.io.IOException
  {
     int i;
     if (maxNextCharInd == 4096)
        maxNextCharInd = nextCharInd = 0;

     try {
        if ((i = inputStream.read(nextCharBuf, maxNextCharInd,
                                            4096 - maxNextCharInd)) == -1)
        {
           inputStream.close();
           throw new java.io.IOException();
        }
        else
           maxNextCharInd += i;
        return;
     }
     catch(java.io.IOException e) {
        if (bufpos != 0)
        {
           --bufpos;
           backup(0);
        }
        else
        {
           bufline[bufpos] = line;
           bufcolumn[bufpos] = column;
        }
        throw e;
     }
  }

Answer 1

您可以使用自定义FilterReader。

class YourFilterReader extends FilterReader{
    @Override
    public int read() throws IOException{
        int read;
        do{
            read = super.read();
        } while(read == '@');

        return read; 
    }

    @Override
    public int read(char[] cbuf, int off, int len) throws IOException{
        int read = super.read(cbuf, off, len);

        if (read == -1) {
            return -1;
        }

        int pos = off - 1;
        for (int readPos = off; readPos < off + read; readPos++) {
            if (read == '@') {
                continue;
            } else {
                pos++;
            }

            if (pos < readPos) {
                cbuf[pos] = cbuf[readPos];
            }
        }
        return pos - off + 1;
    }
}

---

资源：

• Javadoc - FilterReader
• BCRDF - Skipping Invalid XML Character with ReaderFilter

关于同一主题：

• filter/remove invalid xml characters from stream

Answer 2

所有这些读取器、写入器和流都实现了 Decorator 模式。每个装饰器都会为底层实现添加额外的行为和功能。

满足您需求的解决方案可能是 FilterReader：

public class FilterReader implements Readable, Closeable {
  private Set<Character> blacklist = new HashSet<Character>();
  private Reader reader;      

  public FilterReader(Reader reader) {
    this.reader = reader;
  }

  public void addFilter(char filtered) {
    blacklist.add(filtered);
  }

  @Override
  public void close() throws IOException {reader.close();}

  @Override
  public int read(char[] charBuf) {
    char[] temp = new char[charBuf.length];
    int charsRead = reader.read(temp);
    int index = -1;
    if (!(charsRead == -1)) {
      for (char c:temp) {
        if (!blacklist.contains(c)) {
          charBuf[index] = c;
          index++;
         }
      }
    }
    return index;
  }

}

---

注意 - java.io.FilterReader 类是一个零功能的装饰器。您可以扩展它或忽略它并创建自己的装饰器（在这种情况下我更喜欢）。

Answer 3

您可以实现从 InputStream 派生的自己的输入流。然后重写 read 方法，以便它们从流中过滤掉一个特殊字符。

Answer 4

private final void FillBuff() throws java.io.IOException
{
 int i;
 if (maxNextCharInd == 4096)
    maxNextCharInd = nextCharInd = 0;

 try {
    Reader filterReader = new FilterReader(inputStream) {
        public int read() {
            do {
                result = super.read();
            } while (specialCharacter(result));
            return result;
        }
    };
    if ((i = filterReader.read(nextCharBuf, maxNextCharInd,
                                        4096 - maxNextCharInd)) == -1)
    {
       inputStream.close();
       throw new java.io.IOException();
    }
    else
       maxNextCharInd += i;
    return;
 }
 catch(java.io.IOException e) {
    if (bufpos != 0)
    {
       --bufpos;
       backup(0);
    }
    else
    {
       bufline[bufpos] = line;
       bufcolumn[bufpos] = column;
    }
    throw e;
 }
}