去除文件首行BOM字符

package utils;
/**
version: 1.1 / 2007-01-25
- changed BOM recognition ordering (longer boms first)

Original pseudocode   : Thomas Weidenfeller
Implementation tweaked: Aki Nieminen

http://www.unicode.org/unicode/faq/utf_bom.html
BOMs in byte length ordering:
  00 00 FE FF    = UTF-32, big-endian
  FF FE 00 00    = UTF-32, little-endian
  EF BB BF       = UTF-8,
  FE FF          = UTF-16, big-endian
  FF FE          = UTF-16, little-endian

Win2k Notepad:
  Unicode format = UTF-16LE
***/

import java.io.*;

/**
 * This inputstream will recognize unicode BOM marks and will skip bytes if
 * getEncoding() method is called before any of the read(...) methods.
 *
 * Usage pattern: String enc = "ISO-8859-1"; // or NULL to use systemdefault
 * FileInputStream fis = new FileInputStream(file); UnicodeInputStream uin = new
 * UnicodeInputStream(fis, enc); enc = uin.getEncoding(); // check and skip
 * possible BOM bytes InputStreamReader in; if (enc == null) in = new
 * InputStreamReader(uin); else in = new InputStreamReader(uin, enc);
 */
public class UnicodeInputStream extends InputStream {
	PushbackInputStream internalIn;
	boolean isInited = false;
	String defaultEnc;
	String encoding;

	private static final int BOM_SIZE = 4;

	UnicodeInputStream(InputStream in, String defaultEnc) {
		internalIn = new PushbackInputStream(in, BOM_SIZE);
		this.defaultEnc = defaultEnc;
	}

	public String getDefaultEncoding() {
		return defaultEnc;
	}

	public String getEncoding() {
		if (!isInited) {
			try {
				init();
			} catch (IOException ex) {
				IllegalStateException ise = new IllegalStateException("Init method failed.");
				ise.initCause(ise);
				throw ise;
			}
		}
		return encoding;
	}

	/**
	 * Read-ahead four bytes and check for BOM marks. Extra bytes are unread
	 * back to the stream, only BOM bytes are skipped.
	 */
	protected void init() throws IOException {
		if (isInited)
			return;

		byte bom[] = new byte[BOM_SIZE];
		int n, unread;
		n = internalIn.read(bom, 0, bom.length);

		if ((bom[0] == (byte) 0x00) && (bom[1] == (byte) 0x00) && (bom[2] == (byte) 0xFE) && (bom[3] == (byte) 0xFF)) {
			encoding = "UTF-32BE";
			unread = n - 4;
		} else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE) && (bom[2] == (byte) 0x00)
				&& (bom[3] == (byte) 0x00)) {
			encoding = "UTF-32LE";
			unread = n - 4;
		} else if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB) && (bom[2] == (byte) 0xBF)) {
			encoding = "UTF-8";
			unread = n - 3;
		} else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) {
			encoding = "UTF-16BE";
			unread = n - 2;
		} else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) {
			encoding = "UTF-16LE";
			unread = n - 2;
		} else {
			// Unicode BOM mark not found, unread all bytes
			encoding = defaultEnc;
			unread = n;
		}
		// System.out.println("read=" + n + ", unread=" + unread);

		if (unread > 0)
			internalIn.unread(bom, (n - unread), unread);

		isInited = true;
	}

	public void close() throws IOException {
		// init();
		isInited = true;
		internalIn.close();
	}

	public int read() throws IOException {
		// init();
		isInited = true;
		return internalIn.read();
	}
}

package utils;

/**
version: 1.1 / 2007-01-25
- changed BOM recognition ordering (longer boms first)

Original pseudocode   : Thomas Weidenfeller
Implementation tweaked: Aki Nieminen

http://www.unicode.org/unicode/faq/utf_bom.html
BOMs:
  00 00 FE FF    = UTF-32, big-endian
  FF FE 00 00    = UTF-32, little-endian
  EF BB BF       = UTF-8,
  FE FF          = UTF-16, big-endian
  FF FE          = UTF-16, little-endian

Win2k Notepad:
  Unicode format = UTF-16LE
***/

import java.io.*;

/**
 * Generic unicode textreader, which will use BOM mark to identify the encoding
 * to be used. If BOM is not found then use a given default or system encoding.
 */
public class UnicodeReader extends Reader {
	PushbackInputStream internalIn;
	InputStreamReader internalIn2 = null;
	String defaultEnc;

	private static final int BOM_SIZE = 4;

	/**
	 *
	 * @param in
	 *            inputstream to be read
	 * @param defaultEnc
	 *            default encoding if stream does not have BOM marker. Give NULL
	 *            to use system-level default.
	 */
	UnicodeReader(InputStream in, String defaultEnc) {
		internalIn = new PushbackInputStream(in, BOM_SIZE);
		this.defaultEnc = defaultEnc;
	}

	public String getDefaultEncoding() {
		return defaultEnc;
	}

	/**
	 * Get stream encoding or NULL if stream is uninitialized. Call init() or
	 * read() method to initialize it.
	 */
	public String getEncoding() {
		if (internalIn2 == null)
			return null;
		return internalIn2.getEncoding();
	}

	/**
	 * Read-ahead four bytes and check for BOM marks. Extra bytes are unread
	 * back to the stream, only BOM bytes are skipped.
	 */
	protected void init() throws IOException {
		if (internalIn2 != null)
			return;

		String encoding;
		byte bom[] = new byte[BOM_SIZE];
		int n, unread;
		n = internalIn.read(bom, 0, bom.length);

		if ((bom[0] == (byte) 0x00) && (bom[1] == (byte) 0x00) && (bom[2] == (byte) 0xFE) && (bom[3] == (byte) 0xFF)) {
			encoding = "UTF-32BE";
			unread = n - 4;
		} else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE) && (bom[2] == (byte) 0x00)
				&& (bom[3] == (byte) 0x00)) {
			encoding = "UTF-32LE";
			unread = n - 4;
		} else if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB) && (bom[2] == (byte) 0xBF)) {
			encoding = "UTF-8";
			unread = n - 3;
		} else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) {
			encoding = "UTF-16BE";
			unread = n - 2;
		} else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) {
			encoding = "UTF-16LE";
			unread = n - 2;
		} else {
			// Unicode BOM mark not found, unread all bytes
			encoding = defaultEnc;
			unread = n;
		}
		// System.out.println("read=" + n + ", unread=" + unread);

		if (unread > 0)
			internalIn.unread(bom, (n - unread), unread);

		// Use given encoding
		if (encoding == null) {
			internalIn2 = new InputStreamReader(internalIn);
		} else {
			internalIn2 = new InputStreamReader(internalIn, encoding);
		}
	}

	public void close() throws IOException {
		init();
		internalIn2.close();
	}

	public int read(char[] cbuf, int off, int len) throws IOException {
		init();
		return internalIn2.read(cbuf, off, len);
	}

}

package utils;

import com.xiaoleilu.hutool.io.FileUtil;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.util.ArrayList;

/**
 * Created by DimonHo on 2017/12/27.
 */
public class FileUtils extends FileUtil {

    /**
     * 按行读取文件全部内容
     * @param file
     * @return 注意文件首行第一个字符实际上会有一个空字符，表示文件BOM。
     */
    public static ArrayList
 
   readBomLines(File file){
        ArrayList
  
    lines = new ArrayList
   
    (); try { //FileReader reader = new FileReader(file); //会有首行bom字符问题存在，改用下面的方法，可避免首行第一个bom字符问题。 UnicodeReader r = new UnicodeReader(new FileInputStream(file), null); BufferedReader bufferedReader = new BufferedReader(r); String str = null; while((str = bufferedReader.readLine()) != null) { lines.add(str); } bufferedReader.close(); r.close(); } catch (Exception e) { e.printStackTrace(); } return lines; } }