A step solver for my app, Addathon.

Solver.java

package com.erezbiox1;

import com.sun.javaws.exceptions.InvalidArgumentException;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Erezbiox1 on 17/08/2017.
 * (C) 2016 Erez Rotem All Rights Reserved.
 */

public class Solver {

    private int mainNumber = 0;
    private int[] array = new int[9];

    private int last = 0;

    private int[] result = null;

    public Solver(int mainNumber) {
        this.mainNumber = mainNumber;
    }

    public Solver row(int... row) throws InvalidArgumentException {
        return row(row[0], row[1], row[2]);
    }

    public Solver row(int start, int middle, int end) throws InvalidArgumentException {
        if(last > 8)
            error("Row function can only be executed 3 times.");

        array[last++] = start;
        array[last++] = middle;
        array[last++] = end;

        return this;
    }

    public Solver solve() throws InvalidArgumentException {
        if(last != 8)
            error("Row function have be executed 3 times.");

        result = solve(mainNumber, array);
        return this;
    }

    public int[] getOrganized(){
        int[] preArray = array, finalArray = new int[9];
        List<Integer> list = getList(result);

        while(true) {

            int index = 0;

            for (int i : list) {
                for (int j = 0; j < preArray.length; j++)
                    if (preArray[j] == i)
                        index = j;
            }

            Integer number = preArray[index];

            list.remove(Integer.valueOf(number));
            preArray[index] = 0;

            finalArray[index] = number;

            if(list.isEmpty())
                break;
        }

        return finalArray;
    }

    public Solver print(){
        int[] array = getOrganized();
        System.out.println(array[0] + " " + array[1] + " " + array[2]);
        System.out.println(array[3] + " " + array[4] + " " + array[5]);
        System.out.println(array[6] + " " + array[7] + " " + array[8]);
        return this;
    }

    public Solver printRaw(){
        System.out.println(combine(getRaw()));
        return this;
    }

    public int[] getRaw(){
        return result;
    }

    private static int[] solve(int mainNumber, int... numbers){
        int[] array = {0, 0, 0, 0, 0, 0, 0, 0, 0};

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    if(
                                    numbers[a] +
                                    numbers[b]
                                    == mainNumber
                            ){
                        array[0] = numbers[a];
                        array[1] = numbers[b];
                        return array;
                    }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            if(
                                            numbers[a] +
                                            numbers[b] +
                                            numbers[c]
                                            == mainNumber
                                    ){
                                array[0] = numbers[a];
                                array[1] = numbers[b];
                                array[2] = numbers[c];
                                return array;
                            }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    if(
                                                    numbers[a] +
                                                    numbers[b] +
                                                    numbers[c] +
                                                    numbers[d]
                                                    == mainNumber
                                            ){
                                        array[0] = numbers[a];
                                        array[1] = numbers[b];
                                        array[2] = numbers[c];
                                        array[3] = numbers[d];
                                        return array;
                                    }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    for (int e = 0; e < 9; e++)
                                        if(!(e == a || e == b || e == c || e == d))
                                            if(
                                                            numbers[a] +
                                                            numbers[b] +
                                                            numbers[c] +
                                                            numbers[d] +
                                                            numbers[e]
                                                            == mainNumber
                                                    ){
                                                array[0] = numbers[a];
                                                array[1] = numbers[b];
                                                array[2] = numbers[c];
                                                array[3] = numbers[d];
                                                array[4] = numbers[e];
                                                return array;
                                            }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    for (int e = 0; e < 9; e++)
                                        if(!(e == a || e == b || e == c || e == d))
                                            for (int f = 0; f < 9; f++)
                                                if(!(f == a || f == b || f == c || f == d || f == e))
                                                    if(
                                                                    numbers[a] +
                                                                    numbers[b] +
                                                                    numbers[c] +
                                                                    numbers[d] +
                                                                    numbers[e] +
                                                                    numbers[f]
                                                                    == mainNumber
                                                            ){
                                                        array[0] = numbers[a];
                                                        array[1] = numbers[b];
                                                        array[2] = numbers[c];
                                                        array[3] = numbers[d];
                                                        array[4] = numbers[e];
                                                        array[5] = numbers[f];
                                                        return array;
                                                    }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    for (int e = 0; e < 9; e++)
                                        if(!(e == a || e == b || e == c || e == d))
                                            for (int f = 0; f < 9; f++)
                                                if(!(f == a || f == b || f == c || f == d || f == e))
                                                    for (int g = 0; g < 9; g++)
                                                        if(!(g == a || g == b || g == c || g == d || g == e || g == f))
                                                            if(
                                                                            numbers[a] +
                                                                            numbers[b] +
                                                                            numbers[c] +
                                                                            numbers[d] +
                                                                            numbers[e] +
                                                                            numbers[f] +
                                                                            numbers[g]
                                                                            == mainNumber
                                                                    ){
                                                                array[0] = numbers[a];
                                                                array[1] = numbers[b];
                                                                array[2] = numbers[c];
                                                                array[3] = numbers[d];
                                                                array[4] = numbers[e];
                                                                array[5] = numbers[f];
                                                                array[6] = numbers[g];
                                                                return array;
                                                            }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    for (int e = 0; e < 9; e++)
                                        if(!(e == a || e == b || e == c || e == d))
                                            for (int f = 0; f < 9; f++)
                                                if(!(f == a || f == b || f == c || f == d || f == e))
                                                    for (int g = 0; g < 9; g++)
                                                        if(!(g == a || g == b || g == c || g == d || g == e || g == f))
                                                            for (int h = 0; h < 9; h++)
                                                                if(!(h == a || h == b || h == c || h == d || h == e || h == f || h == g))
                                                                    if(
                                                                                    numbers[a] +
                                                                                    numbers[b] +
                                                                                    numbers[c] +
                                                                                    numbers[d] +
                                                                                    numbers[e] +
                                                                                    numbers[f] +
                                                                                    numbers[g] +
                                                                                    numbers[h]
                                                                                    == mainNumber
                                                                            ){
                                                                        array[0] = numbers[a];
                                                                        array[1] = numbers[b];
                                                                        array[2] = numbers[c];
                                                                        array[3] = numbers[d];
                                                                        array[4] = numbers[e];
                                                                        array[5] = numbers[f];
                                                                        array[6] = numbers[g];
                                                                        array[7] = numbers[h];
                                                                        return array;
                                                                    }

        for (int a = 0; a < 9; a++)
            for (int b = 0; b < 9; b++)
                if(a != b)
                    for (int c = 0; c < 9; c++)
                        if(!(c == a || c == b))
                            for (int d = 0; d < 9; d++)
                                if(!(d == a || d == b || d == c))
                                    for (int e = 0; e < 9; e++)
                                        if(!(e == a || e == b || e == c || e == d))
                                            for (int f = 0; f < 9; f++)
                                                if(!(f == a || f == b || f == c || f == d || f == e))
                                                    for (int g = 0; g < 9; g++)
                                                        if(!(g == a || g == b || g == c || g == d || g == e || g == f))
                                                            for (int h = 0; h < 9; h++)
                                                                if(!(h == a || h == b || h == c || h == d || h == e || h == f || h == g))
                                                                    for (int i = 0; i < 9; i++)
                                                                        if(!(i == a || i == b || i == c || i == d || i == e || i == f || i == g || i == h))
                                                                            if(
                                                                                            numbers[a] +
                                                                                            numbers[b] +
                                                                                            numbers[c] +
                                                                                            numbers[d] +
                                                                                            numbers[e] +
                                                                                            numbers[f] +
                                                                                            numbers[g] +
                                                                                            numbers[h] +
                                                                                            numbers[i]
                                                                                            == mainNumber
                                                                                    ){
                                                                                array[0] = numbers[a];
                                                                                array[1] = numbers[b];
                                                                                array[2] = numbers[c];
                                                                                array[3] = numbers[d];
                                                                                array[4] = numbers[e];
                                                                                array[5] = numbers[f];
                                                                                array[6] = numbers[g];
                                                                                array[7] = numbers[h];
                                                                                array[8] = numbers[i];
                                                                                return array;
                                                                            }

        return array;
    }

    private static List<Integer> getList(int[] array){
        List<Integer> list = new ArrayList<>();
        for (int i : array) {
            list.add(i);
        }
        return list;
    }

    private static void error(String... errors) throws InvalidArgumentException {
        throw new InvalidArgumentException(errors);
    }

    private static String combine(int[] array){
        StringBuilder builder = new StringBuilder();
        for (int o : array)
            builder.append(o + " ");
        return builder.toString().trim().replaceAll(" ", ", ") + ".";
    }
}