День добрый, что не так в выражении?
package com.javarush.task.task19.task1908;
/*
Выделяем числа
*/
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String fileNameInput = reader.readLine();
String fileNameOutput = reader.readLine();
reader.close();
StringBuilder sb = new StringBuilder();
BufferedReader readerFile = new BufferedReader(new FileReader(fileNameInput));
while (readerFile.ready()) {
sb.append(readerFile.readLine()).append(System.lineSeparator());
}
readerFile.close();
Pattern pattern = Pattern.compile("[^a-zA-Z]\\d+([^a-zA-Z]|\\n)");
Matcher matcher = pattern.matcher(sb);
BufferedWriter writer = new BufferedWriter(new FileWriter(fileNameOutput));
while (matcher.find()) {
writer.write(sb.substring(matcher.start(), matcher.end()).trim() + " ");
}
writer.close();
}
}