import java.io.FileInputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
public static void main(String[] argv) throws Exception {
Pattern pattern = Pattern.compile("pattern");
FileInputStream input = new FileInputStream("file.txt");
FileChannel channel = input.getChannel();
ByteBuffer bbuf = channel.map(FileChannel.MapMode.READ_ONLY, 0, (int) channel.size());
CharBuffer cbuf = Charset.forName("8859_1").newDecoder().decode(bbuf);
Matcher matcher = pattern.matcher(cbuf);
while (matcher.find()) {
String match = matcher.group();
System.out.println(match);
}
}
}