Я проверял, все работает
package com.javarush.task.task19.task1923;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.*;
import java.io.IOException;
/*
Слова с цифрами
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new FileReader(args[0]));
BufferedWriter writer = new BufferedWriter(new FileWriter(args[1]));
while (reader.ready()) {
String str = reader.readLine();
String newStr = "";
String[] strArr = str.split(" ");
for (String word : strArr) {
char[] wordArr = word.toCharArray();
for (char symbol : wordArr) {
if (Character.isDigit(symbol)) {
newStr = newStr + word + " ";
}
}
}
writer.write(newStr);
newStr = "";
}
writer.close();
reader.close();
}
}