从文件中读取并存储到数组中

Question

I have a project that I am working on that is a maze solver, but I'm trying to figure out the read in from a file and storing it into an array. Most of the stuff that I have looked up to, they work with a created array by them in the program, while mine requires me to read from a file and construct it from there. So far, I have this:

       File map = new File("/Users/michelmaza/Downloads/Project1Map.txt"); //create an object of the file we are reading in
       Scanner scanner = new Scanner(map); //create scanner to read file in
       LinkedList<String> mapping = new LinkedList<String>();//create array list to store the reading from the file

       while (scanner.hasNextLine()) {
            mapping.add(scanner.nextLine()); //Stores the file into the string where every 10 number is a new line
        }
        System.out.println(mapping); //test to see if it works.
        scanner.close(); //close the scanner since its not used anymore.
        } 
        catch (FileNotFoundException e) { //catch in case the file is not found.
        System.out.println("There was no file found, please try again.");
        e.printStackTrace();
        }

When I output it, it throws me a whole array in a line, but I am trying to get in a map format basically a grid 10x10. Any tips or any advice on how I can approach this problem are welcome.

output as of right now [2 3 3 0 0 0 1 0 0 3, 3 0 0 0 0 0 0 3 0 3, 3 3 0 0 0 0 3 3 0 3, 3 3 0 0 0 0 0 0 0 0, 3 3 0 0 0 0 3 3 3 3, 3 3 0 0 0 3 3 3 3 3, 3 3 0 0 3 3 3 3 3 3, 3 3 0 0 3 3 3 3 3 3, 3 3 0 0 3 3 3 3 3 3, 3 3 3 2 3 3 3 3 3 3]

output wanted is

{2, 3, 3, 0, 0, 0, 1, 0, 0, 3},
{3, 0, 0, 0, 0, 0, 0, 3, 0, 3},
{3, 3, 0, 0, 0, 0, 3, 3, 0, 3},
{3, 3, 0, 0, 0, 0, 0, 0, 0, 0},
{3, 3, 0, 0, 0, 0, 3, 3, 3, 3},
{3, 3, 0, 0, 0, 3, 3, 3, 3, 3},
{3, 3, 0, 0, 3, 3, 3, 3, 3, 3},
{3, 3, 0, 0, 3, 3, 3, 3, 3, 3},
{3, 3, 0, 0, 3, 3, 3, 3, 3, 3},
{3, 3, 3, 2, 3, 3, 3, 3, 3, 3}

Answer 1

Hello I wrote a small example for your problem. Hope it will be useful for you.

In map.txt

2 3 3 0 0 0 1 0 0 3 3 0 0 0 0 0 0 3 0 3 3 3 0 0 0 0 3 3 0 3 3 3 0 0 0 0 0 0 0 0 3 3 0 0 0 0 3 3 3 3 3 3 0 0 0 3 3 3 3 3 3 3 0 0 3 3 3 3 3 3 3 3 0 0 3 3 3 3 3 3 3 3 0 0 3 3 3 3 3 3 3 3 3 2 3 3 3 3 3 3

Code:

public static void main(String[] args) {
    final int mapSize = 10;
    List<List<String>> map = new ArrayList<>();
    BufferedReader reader = null;
    try {
        reader = new BufferedReader(new FileReader("F:\\map.txt"));
        String line = reader.readLine();
        if(line != null && !line.isEmpty()) {
            for (int i = 0; i < mapSize; i++) {
                map.add(i, new ArrayList<>());
                String substring = line.trim().substring(0, mapSize * 2 - 1); // 2 for whitespaces
                line = line.trim().substring(mapSize * 2 - 1);
                map.get(i).addAll(Arrays.asList(substring.split(" ")));
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (reader != null) {
                reader.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    for(List<String> row : map) {
        System.out.println(String.join(",", row));
    }
}

Output:

2,3,3,0,0,0,1,0,0,3
3,0,0,0,0,0,0,3,0,3
3,3,0,0,0,0,3,3,0,3
3,3,0,0,0,0,0,0,0,0
3,3,0,0,0,0,3,3,3,3
3,3,0,0,0,3,3,3,3,3
3,3,0,0,3,3,3,3,3,3
3,3,0,0,3,3,3,3,3,3
3,3,0,0,3,3,3,3,3,3
3,3,3,2,3,3,3,3,3,3

Answer 2

Since your input file and expected output was not clear to me, I concentrate on reading the file, I am hoping each line already has 10 strings and has 10 lines to give you your grid

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;

class Scratch {
    public static void main(String[] args) throws IOException {
        List<String> allLinesInFile = Files.readAllLines(Paths.get("/tmp/maze.input"));
        String[] asArray = allLinesInFile.toArray(new String[0]);
        System.out.println(Arrays.toString(asArray));
    }
}

---

Update: Since now the inputs and outputs are clear, here is the full code:)

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.stream.Collectors;

import static java.util.stream.Collectors.*;

class Scratch {
    public static void main(String[] args) throws IOException {
        Path mazeInputFile = Paths.get("/tmp/maze.input");
        Files.writeString(mazeInputFile, "2 3 3 0 0 0 1 0 0 3\n", StandardOpenOption.TRUNCATE_EXISTING);
        Files.writeString(mazeInputFile, "3 0 0 0 0 0 0 3 0 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 0 0 3 3 0 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 0 0 0 0 0 0\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 0 0 3 3 3 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 0 3 3 3 3 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 3 3 3 3 3 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 3 3 3 3 3 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 0 0 3 3 3 3 3 3\n", StandardOpenOption.APPEND);
        Files.writeString(mazeInputFile, "3 3 3 2 3 3 3 3 3 3\n", StandardOpenOption.APPEND);

        System.out.printf("Wrote mazeInputFile = %s\n", mazeInputFile);

        System.out.printf("Reading all Lines From Input file : %s\n", mazeInputFile);
        String[][] mazeInputArray = Files.lines(mazeInputFile) // Gives The lines in file as a Stream
                .filter(line -> line != null && !line.isBlank()) // Filter out unwanted Lines
                .map(line -> line.split(" ", 10)) // Split the line by Space with a maximum of 10 columns
                .toArray(String[][]::new); // Collect as a 2 dimensional Array
        System.out.println("-- --");


        System.out.println("-- Print the Array using a Java 8 Streams (my preference) --");
        String printableMaze = java.util.Arrays.stream(mazeInputArray).
                map(rows -> java.util.Arrays.stream(rows).
                        map(row -> String.join(",", row)). // join each row with a comma
                        collect(joining(",", "{", "}"))). // surround the row with a prefix { and suffix } and join the columns with a comma
                collect(joining(",\n")); // join each row with a leading comma and a newline
        System.out.printf("%s\n", printableMaze);
        System.out.println("-- --");
        System.out.println("-- Here, actually the reading of the file and printing can be combined to read huge files as well without taking too much memory --");
        System.out.println("-- --");

        System.out.println("-- Print the Array using good old for each loops, code looks kind of better but last comma remains --");
        for (String[] rows : mazeInputArray) {
            System.out.print("{");
            System.out.print(String.join(",", rows));
            System.out.print("},\n"); // needs ugly imperative code to get rid of the last comma :P
        }
        System.out.println("-- --");
    }
}

The Output looks like

Wrote mazeInputFile = /tmp/maze.input
Reading all Lines From Input file : /tmp/maze.input
-- --
-- Print the Array using a Java 8 Streams (my preference) --
{2,3,3,0,0,0,1,0,0,3},
{3,0,0,0,0,0,0,3,0,3},
{3,3,0,0,0,0,3,3,0,3},
{3,3,0,0,0,0,0,0,0,0},
{3,3,0,0,0,0,3,3,3,3},
{3,3,0,0,0,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,3,2,3,3,3,3,3,3}
-- --
-- Here, actually the reading of the file and printing can be combined to read huge files as well without taking too much memory --
-- --
-- Print the Array using good old for each loops, code looks kind of better but last comma remains --
{2,3,3,0,0,0,1,0,0,3},
{3,0,0,0,0,0,0,3,0,3},
{3,3,0,0,0,0,3,3,0,3},
{3,3,0,0,0,0,0,0,0,0},
{3,3,0,0,0,0,3,3,3,3},
{3,3,0,0,0,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,0,0,3,3,3,3,3,3},
{3,3,3,2,3,3,3,3,3,3},
-- --

Process finished with exit code 0

• I am not sure what you are looking to do but printing it is different from processing it.
• Why I kept it separate is because you can simply use the mazeInputArray for actually doing something with the input
• Printing is a PIA, using streams makes it easier to NOT think about edge cases as they are intelligently / implicitly handled.