如何使“缩放”功能在二维字符数组中显示边界外的方块

问题描述

基本上，我必须实现多种方法来处理类的二维字符数组（显示、重新着色和缩放）。除了一个问题之外，我已经完成了所有工作 - “缩放”功能旨在显示所选字符及其周围的所有字符，但在没有任何内容可显示的地方显示空白区域。但是我不知道如何让它做到这一点（目前，如果我尝试“放大”到数组边缘周围的任何字符，它只会显示一条错误消息。

下面的代码，我去掉了所有不相关的东西，只留下了显示 (d) 和缩放 (z) 功能。需要明确的是，问题不在于输入超出范围的初始坐标，实际上还有另一种方法可以处理我删除的问题，问题在于“放大”到边缘周围的空间数组，当它尝试显示越界空间时将返回错误消息。

代码：

import java.util.Scanner;

public class CharMapFORHELP {
    public static void zoom(char[][] map,int row,int col) {
        //the problem method
        System.out.print(map[row - 1][col - 1]);
        System.out.print(map[row - 1][col]);
        System.out.print(map[row - 1][col + 1]);
        System.out.println();
        System.out.print(map[row][col - 1]);
        System.out.print(map[row][col]);
        System.out.print(map[row][col + 1]);
        System.out.println();
        System.out.print(map[row + 1][col - 1]);
        System.out.print(map[row + 1][col]);
        System.out.print(map[row + 1][col + 1]);
        System.out.println(); //adds the newline
    }

    /**
     * displays the given character-based map
     * with a leading and trailing blank line.
     */
    public static void displayMap(char[][] map) {
        for (int row = 0; row < map.length; row++) {
            for (int col = 0; col < map[row].length; coL++) {
                System.out.print(map[row][col] + " ");
            }
            System.out.println(); //adds the newline
        }
    }

    // code to convert String array into map. Truthfully
    // I don't 100% understand whats going on here,this
    // was provided to us already written.
    public static char[][] stringToArray(String str) {
        char[][] result;
        String[] rows;

        rows = str.split("\n");
        result = new char[rows.length][];
        for (int r = 0; r < rows.length; r++) {
            result[r] = rows[r].tochararray();
        }
        return result;
    }

    public static void main(String[] args) {
        //Commands
        final char CMD_disPLAY = 'd',CMD_ZOOM = 'z',CMD_QUIT = 'q';
        Scanner sc = new Scanner(system.in);
        char[][] map; // the character-based map
        char command; // user's entered command
        int row;      // |
        int col;      // |- command parameters
        char fill;    // |
        String strMap = "####################\n" +
                        "####           #####\n" +
                        "#                 ##\n" +
                        "##           ###  ##\n" +
                        "######       #######\n" +
                        "##                ##\n" +
                        "####    ##    ##  ##\n" +
                        "######  ######### ##\n" +
                        "####################";

        map = stringToArray(strMap);
        System.out.println("Char Map");
        System.out.println("========");
        System.out.println();
        System.out.println("Enter commands (? for help)." +
                " There are no further prompts after this point.");

        do {
            //read the next single-character command
            command = sc.next().charat(0);
            switch (command) {
                case CMD_disPLAY:
                    displayMap(map);
                    break;
                case CMD_ZOOM:
                    row = sc.nextInt();
                    col = sc.nextInt();
                    zoom(map,row,col);
                    break;
                case CMD_QUIT:
                    break;
            }
        } while (command != CMD_QUIT);
    }
}

解决方法

一种方法是检查数组索引是否越界，然后打印不同的字符。

Wa 可以通过创建一个新方法来检查字符是否越界：

public static String getValue(char[][] map,int row,int col){
    //Check the row
    if (row >= 0 && row < map.length){
        //Check the col
        if(col >= 0 && col < map[row].length){
            //Return the character only if the row and col are valid
            return map[row][col];
        }
    }

    //If the above checks fail then the index is out of bounds.
    //So return a placeholder for printing,in this example we use a dash
    return "-";
}

现在我们可以修改缩放方法以使用 getValue(map,row,col) 方法，如下所示：

public static void zoom(char[][] map,int col) {    
    System.out.print(getValue(map,row - 1,col - 1));
    System.out.print(getValue(map,col));
    System.out.print(getValue(map,col + 1));
    System.out.println();
    System.out.print(getValue(map,row + 1,col + 1));
    System.out.println(); //adds the newline
}