java读取UTF-8文本文件第一个字符多出一个问号解决方法

package com.bigdata.ai.util;
/**
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);
}

}

package com.bigdata.ai.util;

/**
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();
}
}