从 Java 中的位置读取文本文件 [英] Read text file from position in Java

问题描述

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:

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:

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;

有没有更简单的方法?(无需手动匹配char->byte)

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.

I was looking about java.util.Scanner, but it's Iterator-style, and i need random access-style.

PS 数据不应该被多次复制

PS data should'n be copied many times

推荐答案

使用 BufferedReader 的 skip() 方法.在你的情况下:

Use BufferedReader's skip() method. In your case:

BufferedReader reader = new BufferedReader(new FileReader(filePath));
reader.skip(n); // chars to skip
// .. and here you can start reading

如果你想指定一个特定的编码，你可以使用

And if you want specify a particular encoding you can use

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

这篇关于从 Java 中的位置读取文本文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！