java读utf8 的txt文件，第一个字符为空或问号问题

参考：https://blog.csdn.net/yangzhichao888/article/details/79529756

https://blog.csdn.net/wangzhi291/article/details/41485403

1.新建一个类，叫“UnicodeReader”，复制粘贴如下内容;



/**

 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);

   }

}

写入文件时：

    	 PrintWriter out=null;

        try {

        	File filename = new File(savefile);

            filename.createNewFile();

            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(filename),"UTF-8")));

            System.out.println("打开fwriter");

            String []ss = content.split(",");

            out.write("["+"\r\n");

            out.write(s+","+"\r\n");

        } catch (IOException ex)

        {

            ex.printStackTrace();

        }

        finally {

            out.flush();

	out.close();

	System.out.println("关闭fwriter");

        }

    }

巴特西

java读utf8 的txt文件，第一个字符为空或问号问题

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