Вредный валидатор

for (String str : allLines) {
    if (!forRemoveLines.contains(str)) {
        allLines.clear();
        throw  new CorruptedDataException();
    } else {
        allLines.remove(str);
    }
}

public void joinData() throws IOException, CorruptedDataException {

        for (int i = 0; i < 2; i++) {
            String filename = reader.readLine();
            BufferedReader filereader = new BufferedReader(new FileReader(new File(filename)));

            String line = null;

            if (i == 0) {
                while ((line = filereader.readLine()) != null) {
                    allLines.add(line);
                }
            } else {
                while ((line = filereader.readLine()) != null) {
                    forRemoveLines.add(line);
                }
            }
        }
/*
        System.out.println("Массив 1 \n");
        for (int i = 0; i < allLines.size(); i++) {
            System.out.println(allLines.get(i));
        }

        System.out.println("\n Массив 2");

        for (int i = 0; i < forRemoveLines.size(); i++) {
            System.out.println(forRemoveLines.get(i));
        }
*/

        for (String str : forRemoveLines) {
            if (!allLines.contains(str)) {
                allLines.clear();
                throw new CorruptedDataException();
            } else {
                allLines.remove(str);
            }
        }
    }

String filename = reader.readLine();
        String filename1 = reader.readLine();

        BufferedReader filereader = new BufferedReader(new FileReader(new File(filename)));
        BufferedReader filereader1 = new BufferedReader(new FileReader(new File(filename1)));

        String line = null;

        while ((line = filereader.readLine()) != null) {
            allLines.add(line);
        }
        while ((line = filereader1.readLine()) != null) {
            forRemoveLines.add(line);
        }

package com.javarush.task.task17.task1721;

import org.w3c.dom.ls.LSOutput;

import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/*
Транзакционность
*/

public class Solution {
    public static List<String> allLines = new ArrayList<String>();
    public static List<String> forRemoveLines = new ArrayList<String>();

    public static void main(String[] args) {
        try {
            new Solution().joinData();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public void joinData() throws IOException, CorruptedDataException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));


        String filename = reader.readLine();
        String filename1 = reader.readLine();

        BufferedReader filereader = new BufferedReader(new FileReader(filename));
        BufferedReader filereader1 = new BufferedReader(new FileReader(filename1));

        String line = null;

        while ((line = filereader.readLine()) != null) {
            allLines.add(line);
        }
        while ((line = filereader1.readLine()) != null) {
            forRemoveLines.add(line);
        }
/*
        System.out.println("Массив 1 \n");
        for (int i = 0; i < allLines.size(); i++) {
            System.out.println(allLines.get(i));
        }

        System.out.println("\n Массив 2");

        for (int i = 0; i < forRemoveLines.size(); i++) {
            System.out.println(forRemoveLines.get(i));
        }
*/

        for (String str : forRemoveLines)
            if (!allLines.contains(str)) {
                allLines.clear();
                reader.close();
                throw new CorruptedDataException();
            } else {
                allLines.remove(str);
            }
        reader.close();
    }
}

import org.w3c.dom.ls.LSOutput;