Вроде работает правильно, но валидацию не проходит....
package com.javarush.task.task19.task1908;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/*
Выделяем числа
*/
public class Solution {
public static void main(String[] args) throws Exception{
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
String file1 = bufferedReader.readLine();
String file2 = bufferedReader.readLine();
bufferedReader.close();
BufferedReader reader = new BufferedReader(new FileReader(file1));
List<String> words = new ArrayList<>();
while (reader.ready()){
String line = reader.readLine();
for (String a : line.split(" ")){
words.add(a);
}
}
reader.close();
BufferedWriter writer = new BufferedWriter(new FileWriter(file2));
char ch;
for (int i = 0; i < words.size(); i++) {
for (int j = 0; j < words.get(i).length(); j++) {
ch = words.get(i).charAt(j);
if (Character.isUpperCase(ch)) {
words.remove(i);
} else if (Character.isLowerCase(ch)) {
words.remove(i);
}
}
}
for (int i = 0; i < words.size(); i++) {
writer.write(words.get(i) + " ");
}
writer.close();
}
}