检查文件是否是 UTF-8/UTF-16 编码

public class UnicodeUtil
{
public final static String SIGNATURE_UTF_8 = "UTF-8"; //$NON-NLS-1$
public final static String SIGNATURE_UNICODE_BIG = "UnicodeBig"; //$NON-NLS-1$
public final static String SIGNATURE_UNICODE_LITTLE = "UnicodeLittle"; //$NON-NLS-1$
public final static String SIGNATURE_UCS4_BIG = "UCS-4Big"; //$NON-NLS-1$
public final static String SIGNATURE_UCS4_LITTLE = "UCS-4Little"; //$NON-NLS-1$
/**
* @param inputStream
* the input stream of the unicode file
*
* @return the encoding signature from the unicode file.
*
* @throws IOException
* if errors occur when reading bytes from the input stream
*/
public static String checkUTFSignature( InputStream inputStream )
throws IOException
{
inputStream.mark( 1024 );
int byte1 = inputStream.read( );
int byte2 = inputStream.read( );
if ( byte1 == 0xFE && byte2 == 0xFF )
{
return SIGNATURE_UNICODE_BIG;
}
else if ( byte1 == 0xFF && byte2 == 0xFE )
{
return SIGNATURE_UNICODE_LITTLE;
}
int byte3 = inputStream.read( );
// check for UTF-8 byte order mark
if ( byte1 == 0xEF && byte2 == 0xBB && byte3 == 0xBF )
{
return SIGNATURE_UTF_8;
}
int byte4 = inputStream.read( );
if ( byte1 == 0x00 && byte2 == 0x00 && byte3 == 0xFE && byte4 == 0xFF )
{
return SIGNATURE_UCS4_BIG;
}
else if ( byte1 == 0x00 && byte2 == 0x00 && byte3 == 0xFF
&& byte4 == 0xFE )
{
return SIGNATURE_UCS4_LITTLE;
}
inputStream.reset( );
return null; //$NON-NLS-1$
}
}