从 Java 中的位置读取文本文件
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Read text file from position in Java
提问by styanton
I need to read char[] (size is COUNT) from text file from OFFSET with specified Charset. COUNT and OFFSET are in characters, not in bytes. He is my code:
我需要从具有指定字符集的 OFFSET 的文本文件中读取 char[]（大小为 COUNT）。COUNT 和 OFFSET 以字符为单位，而不是以字节为单位。他是我的代码：
raf = new RandomAccessFile(filePath, "r");
if ((mBuffer == null) || (mBuffer.length < count)) {
mBuffer = new byte[(int)(count/mDecoder.averageCharsPerByte())];
mByteWrap = ByteBuffer.wrap(mBuffer);
mCharBuffer = new char[count];
mCharWrap = CharBuffer.wrap(mCharBuffer);
}
try {
offset = (int)(offset/mDecoder.averageCharsPerByte());
count = (int)(count/mDecoder.averageCharsPerByte());
raf.seek(offset);
raf.read(mBuffer,0,count);
mByteWrap.position(0);
mCharWrap.position(0);
mDecoder.decode(mByteWrap, mCharWrap, true);
} catch (IOException e) {
return null;
}
return mCharBuffer;
Is there any way easier ? (without manual matching char->byte)
有没有更简单的方法？（无需手动匹配 char->byte）
I was looking about java.util.Scanner, but it's Iterator-style, and i need random access-style.
我正在寻找 java.util.Scanner，但它是迭代器风格的，我需要随机访问风格。
PS data should'n be copied many times
PS数据不应该被多次复制
采纳答案by dash1e
Use BufferedReader's skip()method.
In your case:
使用 BufferedReader 的skip()方法。在你的情况下：
BufferedReader reader = new BufferedReader(new FileReader(filePath));
reader.skip(n); // chars to skip
// .. and here you can start reading
And if you want specify a particular encoding you can use
如果你想指定一个特定的编码，你可以使用
InputStream is = new FileInputStream(filePath);
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"UTF-8"));
reader.skip(n); // chars to skip
// .. and here you can start reading
回答by Amit
you can use read(byte[] b, int off, int len) of BufferedInputStream
你可以使用 BufferedInputStream 的 read(byte[] b, int off, int len)
here the off is offset (point from where you want to start reading)
这里关闭是偏移量（从你想开始阅读的点）
