Java讀取UTF-8格式txt文件第一行出現亂碼——問號“?”及解決

    今天導入文件的時候,出現?,經過覈查是UTF-8那個BOM的問題,最後經過查找,找了一個比較好的方法解決。

使用一個更強大點的工具類(可以支持UTF-8/UTF-16LE/UTF-16BE/UTF-32LE/UTF-32BE):
       

   參考地址:http://koti.mbnet.fi/akini/java/unicodereader/, 下載其中兩個文件:UnicodeStream和UnicodeReader

   附上這兩個類的代碼,

/**
 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 Test;
/**
 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.
    */
   public 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);
    
}
 
 
}

發表評論
所有評論
還沒有人評論,想成為第一個評論的人麼? 請在上方評論欄輸入並且點擊發布.
相關文章