使用String的JAVA 2D地图？ 即“ +”和“ C”

Question

so I've been looking but I simply just don't know how to state my problem.

So I'm just going to break an egg, and if you can link to the correct answer anyhow then please don't be afraid to, this is a long shot and I know this exists many places, I am just unable to find it.

I am looking at making a 2D map, based off on PLUS signs (+) and ONE (C), the C is the characters current location.

It would look like this

C+++++++++++++++++++
++++++++++++++++++++
++++++++++++++++++++
++++++++++++++++++++
++++++++++++++++++++

When printed. Notice C is based off of integers, namely currentX and currentY (1 & 1).

This is my current code in bp_Map.class

public class bp_Map {
// Map
public static String mapP = "+";
public static String mapC = "C";
public static int sizeY = 19;
public static int sizeX = 19;


public static void drawMap(int currX, int currY) {
    int currentY = 0;

        while (currentY <= sizeY) {
            drawX();
            System.out.print("\n");
            currentY ++;
        }
}

public static void drawX() {
    int currentX = 0;

    while (currentX <= sizeX) {
        System.out.print(mapP);
        currentX++;
    }
}

I could use an array, instead of mapP and mapC and just do

public static final String mapChar[] = {"+", "C"}

But I don't feel the need to do this atm.

My current problem is I don't want 20 if statements (or 1 if and 19 if else statements) to check the location of X, and then print correspondingly Y.

I am new to java and still learning, I have used while, but should I use for? I'm a bit lost, hope you guys can help me. This is for a text-based rpg, and I'm working on it alongside my studies.

Answer 1

An approach I would use in this case is the following in pseudo-code:

1. Create a character matrix with the dimensions of sizeX by sizeY
2. Use the java.util.Arrays.fill builtin to fill the entire matrix with the character '+'
3. Replace the character at position {currX, currY} (1-indexed) with character 'C'
4. Pretty-print the matrix

Here a possible implementation of what I described above:

/*
 * Prints a block of sizeX by sizeY of the filler character,
 * where the character at position {posX, posY} (1-indexed) is replaced with the replacement character
 * 
 * TODO: Validation checks. Currently assumes posX and posY are always within range of the matrix
 */
public void drawMap(int sizeX, int sizeY, char fillerChar, char replacementChar, int posX, int posY){
  // Create a char-matrix of dimensions sizeX by sizeY
  char[][] matrix = new char[sizeX][sizeY];

  // Fill this matrix initially with the filler-character
  for(char[] row : matrix)
    java.util.Arrays.fill(row, fillerChar);

  // Replace the character at position {currX, currY} (1-indexed) with the replacement-character
  matrix[posX-1][posY-1] = replacementChar;

  // Print the matrix
  prettyPrintMatrix(matrix);
}

private void prettyPrintMatrix(char[][] matrix){
  for(char[] row : matrix){
    for(char ch : row)
      System.out.print(ch);
    System.out.println();
  }
}

This could then be called with:

drawMap(10, 10, '+', 'C', 4, 2);

Which will output:

++++++++++
++++++++++
++++++++++
+C++++++++
++++++++++
++++++++++
++++++++++
++++++++++
++++++++++
++++++++++

Try it online.

Some things to note:

1. I've added the size and characters as parameter to the method. In my TIO-link above you can see a call with different sizes or characters also works (ie m.drawMap(5, 5, 'a', 'B', 5, 5); ).
2. I've added a TODO for validation checks. If the given posX or poxY are larger than the sizeX or sizeY respectively, it will of course give an ArrayOutOfBoundsException. So perhaps a check at the top of the method to see if the given pos -parameters are valid is in order depending on how you want to use it.

Answer 2

You don't need if-else cases - this is a perfect usage example for loops .

First of all, define things which will never change as final fields in your class:

private static final String EMPTY = "+";
private static final String CHARACTER = "C";

private static final int SIZE_X = 20;
private static final int SIZE_Y = 5;

For this example, I'll be using fields for the current X and Y coordinates too, but you may want to change this since I assume they come from elsewhere in your program:

private static int currentX = 7;
private static int currentY = 3;

Now, think of how a TV draws pixels on a screen: from the top to the bottom and from left to right, pixel by pixel, at least 30 times a second. Let's try and do the same, and draw one row at a time:

public static void main(String[] args) {
    if(currentX > SIZE_X - 1 || currentY > SIZE_Y - 1) {
        throw new IllegalStateException("Out of bounds");
    }
    for (int y = 0; y < SIZE_Y; y++) {
        drawRow(y);
    }
}

What would the drawRow() function look like? One possible implementation is below:

private static void drawRow(int i) {
    // Use a StringBuilder, ~30 times faster than String concatenation!
    StringBuilder row = new StringBuilder();
    if(i == currentY) {
        // Create this row differently, as it contains the character.
        for (int x = 0; x < SIZE_X; x++) {
            if(x == currentX) {
                row.append(CHARACTER);
            } else {
                row.append(EMPTY);
            }
        }
    } else {
        // Create an empty row.
        for (int x = 0; x < SIZE_X; x++) {
            row.append(EMPTY);
        }
    }
    // "Draw" the row by printing it to the console.
    System.out.println(row.toString());
}

This produces:

++++++++++++++++++++
++++++++++++++++++++
++++++++++++++++++++
+++++++C++++++++++++
++++++++++++++++++++

Try playing around with the coordinates and run main again. This is just one of many possible solutions - the neat thing about the above code is that no Map or even array is needed, but it may be that you do need them eventually and the code would have to change to accommodate this (eg keep a bit matrix, make a nested for loop over it and draw the set bit as the character ). Let us know if you would like an example of this.