MapLoader.java

//  Sokoban state space explorer.
//  Discussion: https://dxdy.ru/topic144781.html

import java.io.*;
import java.util.*;

public class MapLoader {

    private boolean isOpen, hasLines;
    private Scanner inputFile;
    private List <String> linesList;

    public MapLoader () {
        isOpen = false;
        hasLines = false;
        linesList = new ArrayList <> ();
    }

    public boolean hasLines () {
        return hasLines;
    }

    public String [] getMapLines () {
        if (hasLines) {
            return linesList .toArray (new String [linesList .size ()]);
        } else {
            return null;
        }
    }

    public boolean openFile (String fileName) {
        if (isOpen) {
            inputFile .close ();
            linesList .clear ();
            hasLines = false;
        }
        try {
            inputFile = new Scanner (new File (fileName));
        } catch (IOException ex) {
            ex .printStackTrace ();
            isOpen = false;
            return false;
        }
        isOpen = true;
        return true;
    }

    public void closeFile () {
        if (isOpen) {
            inputFile .close ();
            isOpen = false;
        }
    }

    public void skip (int arg) {
        while (0 < arg && loadNext ()) {
            --arg;
        }
    }

    public boolean loadNext () {
        String fileLine;

        linesList .clear ();
        hasLines = false;

        if (!isOpen) {
            return false;
        }

        while (true) {
            if (!inputFile .hasNextLine ()) {
                break;
            }
            fileLine = inputFile .nextLine ();
            if (isMapString (fileLine)) {
                linesList .add (fileLine);
                continue;
            }
            if (2 < linesList .size ()) {
                hasLines = true;
                return true;
            }
            linesList .clear ();
        }

        hasLines = 2 < linesList .size ();
        return hasLines;
    }

    private static boolean isMapString (String arg) {
        int k, length, count;

        length = arg .length ();
        if (3 > length) {
            return false;
        }
        count = 0;
        for (k = 0; length > k; ++k) {
            switch (arg .charAt (k)) {
            case '#':
                ++count;
            case ' ':
            case '$':
            case '*':
            case '+':
            case '.':
            case '@':
                break;
            default:
                return false;
            }
        }
        return 1 < count;
    }

    public static void displayLines (String [] arg) {
        for (int k = 0; arg .length > k; ++k) {
            System .out .println (arg [k]);
        }
    }
}