Нужна подсказка.
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));
BufferedReader fileReader = new BufferedReader(new FileReader(reader.readLine()));
BufferedWriter fileWriter = new BufferedWriter(new FileWriter(reader.readLine()));
String number = null;
reader.close();
while ((number = fileReader.readLine()) != null)
{
Pattern p = Pattern.compile("\b[0-9]+\b");
Matcher m = p.matcher(number);
while (m.find())
{
fileWriter.write(number.substring(m.start(), m.end()));
fileWriter.write(" ");
}
}
fileReader.close();
fileWriter.close();
}
}