java 7 nio逐行读取文件内容

nio逐行读取文件内容，使用 java 7.

首先，获取文件编码；

其次，读取文件内容。

 

1. 获取文件编码

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class CommonsMethods {
	/**
	 * @Title: getFileCharset
	 * @Description: 判断文件的编码格式
	 * @param filePath
	 *            文件绝对路径
	 * @return String
	 * @author 
	 * @date 2015年12月26日
	 */
	public static String getFileCharset(String filePath) {

		File file = new File(filePath);

		if (!file.exists()) {
			System.out.println("File not found.");
		}
		// 默认编码格式为GBK
		String charset = "GBK";

		FileInputStream is = null;
		BufferedInputStream bis = null;

		try {
			byte[] first3Bytes = new byte[3];

			boolean checked = false;

			is = new FileInputStream(file);

			bis = new BufferedInputStream(is);

			bis.mark(0);

			int read = bis.read(first3Bytes, 0, 3);

			if (-1 == read) {
				charset = "GBK";
			} else if (first3Bytes[0] == (byte) 0xFF
					&& first3Bytes[1] == (byte) 0xFE) {
				charset = "UTF-16LE";
				checked = true;
			} else if (first3Bytes[0] == (byte) 0xFE
					&& first3Bytes[1] == (byte) 0xFF) {
				charset = "UTF-16BE";
				checked = true;
			} else if (first3Bytes[0] == (byte) 0xEF
					&& first3Bytes[1] == (byte) 0xBB
					&& first3Bytes[2] == (byte) 0xBF) {
				charset = "UTF-8";
				checked = true;
			}
			bis.reset();

			if (!checked) {

				int loc = 0;

				while ((read = bis.read()) != -1) {

					loc++;

					if (read >= 0xF0) {
						break;
					}

					if (0x80 <= read && read <= 0xBF) {
						// 单独出现BF以下的,也算GBK
						break;
					}

					if (0x80 <= read && read <= 0xDF) {
						read = bis.read();
						if (0x80 <= read && read <= 0xBF) {
							// GBK
							continue;
						} else {
							break;
						}
					} else if (0xE0 <= read && read <= 0xEF) {
						read = bis.read();
						if (0x80 <= read && read <= 0xBF) {
							read = bis.read();
							if (0x80 <= read && read <= 0xBF) {
								charset = "UTF-8";
								break;
							} else {
								break;
							}
						} else {
							break;
						}
					}
				}
			}

		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			IOUtils.closeStream(bis, null);
			IOUtils.closeStream(is, null);
		}

		return charset;
	}
}

 

2. 逐行读取文件内容

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class NioReadFile {

	public static void main(String[] args) {

		String fileName = "D:\\CIME\\measure.CIME";

		String charset = CommonsMethods.getFileCharset(fileName);

		System.out.println("charset=" + charset);

		try {
			List<String> lines = Files.readAllLines(Paths.get(fileName),
					Charset.forName(charset));

			for (String line : lines) {
				System.out.println(line);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

 

3. IOUtils

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.nio.channels.Channel;

public class IOUtils {

	public static void closeStream(InputStream is, OutputStream out) {

		if (null != out) {
			try {
				out.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			out = null;
		}

		if (null != is) {
			try {
				is.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			is = null;
		}
	}

	public static void closeReader(Reader reader) {

		if (null != reader) {
			try {
				reader.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			reader = null;
		}
	}

	public static void closeWriter(Writer writer) {

		if (null != writer) {
			try {
				writer.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			writer = null;
		}
	}

	public static void closeChannel(Channel c) {

		if (null != c) {
			try {
				c.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			c = null;
		}
	}
}