(Java) lab 4.2 Main

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.Iterator;

public class lab4_2 {
    static Scanner scan = new Scanner(System.in);

    static int counter = 0;

    public static void main(String[] args) {
        System.out.print("Welcome to the program\nSelect the source for entering numbers:\n1:Console\n2:File\nEnter 1 or 2: ");
        int inputSource = takeSource();
        String path = "";
        if (inputSource == 2){
            path = takeInPath();
        }
        int n = takeNum(inputSource, path, 1);
        int[] arr = fillArr(n);
        int sum = takeNum(inputSource,path, 2);
        System.out.print("Select the source for output:\n1:Console\n2:File\nEnter 1 or 2: ");
        int outSource = takeSource();
        int[][] answer = new int[1000][n];
        answer = findAllSubsets(arr, n, sum, null, answer);
        output(answer, outSource, n);
    }

    static void output (final int[][] answer, int source, int n){
        String outPath;
        if (source == 1) {
            consoleOutput(answer, n);
        } else {
            outPath = takeOutPath();
            FileOutput(outPath, answer, n);
        }
    }

    static void consoleOutput(final int[][] answer,int n){
        int i = 0;
        int j = 0;
        System.out.println("Answer:");
        while ((j < n) && (answer[i][j] != 0)){
            while ((j < n) && (answer[i][j] != 0)){
                System.out.print("[" + answer[i][j]+"] ");
                j++;
            }
            i++;
            j = 0;
            System.out.println();
        }
    }

    static void FileOutput(final String path, final int[][] answer, int n) {
        try (FileWriter fw = new FileWriter(path)) {
            int i = 0;
            int j = 0;
            fw.write("Answer:\n");
            while ((i < n) && (answer[i][j] != 0)){
                while ((i < n) && (answer[i][j] != 0)){
                    fw.write("[" + answer[i][j]+"] ");
                    j++;
                }
                i++;
                j = 0;
                fw.write("\n");
            }
            System.out.println("Done");
        } catch (Exception e) {
            System.out.println("File error!");
        }
    }

    static int takeSource() {
        final byte CONSOLE = 1;
        final byte FILE = 2;
        boolean isIncorrect;
        byte choice = 0;
        do {
            isIncorrect = false;
            try {
                choice = Byte.parseByte(scan.nextLine());
            } catch (Exception e) {
                System.out.print("Incorrect input!!!\nSelect the source:\n1:Console\n2:File\nEnter 1 or 2: ");
                isIncorrect = true;
            }
            if (!isIncorrect && (choice != CONSOLE) && (choice != FILE)) {
                System.out.print("Incorrect input!!!\nSelect the source:\n1:Console\n2:File\nEnter 1 or 2: ");
                isIncorrect = true;
            }
        } while (isIncorrect);
        return choice;
    }

    static String takeInPath() {
        String path;
        boolean isIncorrect;
        System.out.print("Enter file path: ");
        do {
            isIncorrect = false;
            path = scan.nextLine();
            File file = new File(path);
            if (!file.exists()) {
                System.out.print("File is not found\nEnter file path: ");
                isIncorrect = true;
            }
            if (!isIncorrect && (!path.endsWith(".txt"))) {
                System.out.print("File is found, but it is not \".txt\" type file\nEnter file path: ");
                isIncorrect = true;
            }
        } while (isIncorrect);
        return path;
    }

    static String takeOutPath() {
        String path;
        boolean isIncorrect;
        System.out.print("Enter file path: ");
        do {
            isIncorrect = false;
            path = scan.nextLine();
            if (!path.endsWith(".txt")) {
                System.out.print("It should be a \".txt\" file\nEnter file path: ");
                isIncorrect = true;
            }
        } while (isIncorrect);
        return path;
    }

    private static int[] fillArr(final int n) {
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = i + 1;
        }
        return arr;
    }

    private static int takeNum(final int inputSource, String path, final int goal) {
        int num;
        if (inputSource == 1) {
            num = takeInt(1, (goal == 1) ? 15 : 100, goal);
        } else {
            num = takeNumFromFile(path, goal);
            while (num == 0) {
                path = takeInPath();
                num = takeNumFromFile(path, goal);
            }
        }
        return num;
    }

    private static int takeNumFromFile(final String path, final int goal) {
        final int SET_LINE_N = 1;
        int lineCounter = 0;
        String line;
        boolean isCorrect = true;
        int num = 0;
        try (BufferedReader reader = new BufferedReader(new FileReader(path))) {
            while ((isCorrect) && ((line = reader.readLine()) != null)) {
                lineCounter++;
                if ((lineCounter == SET_LINE_N) && (goal == 1)){
                    try {
                        num = Integer.parseInt(line);
                    } catch (NumberFormatException e) {
                        System.out.println("Incorrect file content!!! Incorrect information in the set line!!!");
                        isCorrect = false;
                    }
                }
                if ((lineCounter == SET_LINE_N + 1) && (goal == 2)){
                    try {
                        num = Integer.parseInt(line);
                    } catch (NumberFormatException e) {
                        System.out.println("Incorrect file content!!! Incorrect information in the set line!!!");
                        isCorrect = false;
                    }
                }
            }
        } catch (IOException e) {
            System.out.println("Input/Output error!!!");
            isCorrect = false;
        }
        if ((isCorrect) && (lineCounter > SET_LINE_N + 1)) {
            System.out.println("Incorrect file content!!!");
            isCorrect = false;
        }
        if (isCorrect) {
            return num;
        } else {
            return 0;
        }
    }

    private static int takeInt(final int min, final int max, final int goal) {
        boolean isIncorrect;
        int num = -1;
        do {
            isIncorrect = false;
            System.out.printf("Enter " + (goal == 1? "n" : "A") + " value in range (%s, %s): \n", min, max);
            try {
                num = Integer.parseInt(scan.nextLine());
            } catch (NumberFormatException e) {
                isIncorrect = true;
            }
            if (!isIncorrect) {
                isIncorrect = num > max || num < min;
            }
            System.out.print(isIncorrect ? "Incorrect input, try again!\n" : "");
        } while (isIncorrect);
        return num;
    }


    static void findSubsetsRec(int[] arr, int i, int sum, ArrayList<Integer> indexes, boolean[][] isFine, int[][] ans) {
        if (i == 0 && sum != 0 && isFine[0][sum]) {
            indexes.add(arr[i]);
            Iterator<Integer> iterator = indexes.iterator();
            for (int k = 0; k < indexes.size(); k++) {
                ans[counter][k] = indexes.get(k);
            }
            counter++;
            indexes.clear();
            return;
        }
        if (i == 0 && sum == 0) {
            Iterator<Integer> iterator = indexes.iterator();
            for (int k = 0; k < indexes.size(); k++) {
                ans[counter][k] = indexes.get(k);
            }
            counter++;
            indexes.clear();
            return;
        }
        if (isFine[i - 1][sum]) {
            ArrayList<Integer> b = new ArrayList<>(indexes);
            findSubsetsRec(arr, i - 1, sum, b, isFine, ans);
        }
        if (sum >= arr[i] && isFine[i - 1][sum - arr[i]]) {
            indexes.add(arr[i]);
            findSubsetsRec(arr, i - 1, sum - arr[i], indexes, isFine, ans);

        }
    }

    static int[][] findAllSubsets(int[] arr, int n, int sum, boolean[][] isFine, int[][] ans) {
        isFine = new boolean[n][sum + 1];
        for (int i = 0; i < n; ++i) {
            isFine[i][0] = true;
        }
        if (arr[0] <= sum)
            isFine[0][arr[0]] = true;
        ArrayList<Integer> p = new ArrayList<>();
        for (int i = 1; i < n; ++i)
            for (int j = 0; j < sum + 1; ++j) {
                if (arr[i] <= j)
                    isFine[i][j] = isFine[i - 1][j] || isFine[i - 1][j - arr[i]];
                else isFine[i][j] = isFine[i - 1][j];
            }
        if (!isFine[n - 1][sum]) {
            findAllSubsets(arr, n, sum - 1, isFine, ans);
            return ans;
        }
        findSubsetsRec(arr, n - 1, sum, p, isFine, ans);
        return ans;
    }
}