I tried it in my ide, and everything works at it should or maybe im not seeing something.
String tekst = "12 text var2 14 8v 1 fss2 3sa123s s123" + "\n" + "231 23axd s 213132sd234r3";
String onlyDecimalsAndSpaces = tekst.replaceAll("[^\\d]+"," ").replaceAll("\\s+"," ").trim();
System.out.println(onlyDecimalsAndSpaces);package pl.codegym.task.task19.task1908;
/*
Wybieranie numerów
*/
import java.io.*;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String file1Name = reader.readLine();
String file2Name = reader.readLine();
reader.close();
BufferedReader bufferedFileReader = new BufferedReader(new FileReader(file1Name));
StringBuilder builder = new StringBuilder();
String line;
while((line = bufferedFileReader.readLine()) != null){
builder.append(line);
}
bufferedFileReader.close();
String allLines = builder.toString();
String onlyDecimalsAndSpaces = allLines.replaceAll("[^\\d]+"," ").replaceAll("\\s+"," ").trim();
BufferedWriter bufferedFileWriter = new BufferedWriter(new FileWriter(file2Name));
bufferedFileWriter.write(onlyDecimalsAndSpaces);
bufferedFileWriter.close();
}
}