本文介绍了从 Java 中的位置读取文本文件的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
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
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