Question

我正在为分配该程序，而我绝对不知道为什么我的数组（从单独的文件中读取值）不能满足此if语句的条件。为方便起见，有问题的语句位于displayColonies类中。

当我读入数组时，它会在指定的行和列中查找值，这是从1到9范围内的int值。当我使用print语句定期测试时，该数组确实包含正确的值，但是if语句从未激活。条件与数组的值匹配，但不会对语句进行true或其他方式的评估。

感谢您的帮助。

代码附在下面： DetectColonies2ElectricBoogaloo是客户端幻灯片是对象 slide.dat是文本文件，排列如下

public class DetectColonies2ElectricBoogaloo {

    public static void main(String [] args) {

        Slide culture = new Slide("Slide.dat");
        culture.displaySlide();
        culture.displayColonies();
   }
}

import java.io.*;

public class Slide {

    private char NON_COLONY = '0';
    private char [][] slideData;

    /**
     * constructor
     * pre: Slide file contains valid slide data in the format:
     * first line: lenght of slide
     * second line: width of slide
     * remaining lines: slide data
     * post: Slide data has been loaded from slide file.
     */
    public Slide(String s) {    
        try {
            File slideFile = new File(s);
            FileReader in = new FileReader(slideFile);
            BufferedReader readSlide = new BufferedReader(in);

            int length = Integer.parseInt(readSlide.readLine());
            int width = Integer.parseInt(readSlide.readLine());
            slideData = new char[length][width];

            for (int row = 0; row < length; row++) {
                for (int col = 0; col < width; col++) {
                    slideData[row][col] = (char)readSlide.read();
                }
                readSlide.readLine();   //read past end-of-line characters
            }
            readSlide.close();
            in.close();
       } catch (FileNotFoundException e) {
            System.out.println("File does not exist or could not be found.");
            System.err.println("FileNotFoundException: " + e.getMessage());
        } catch (IOException e) {
            System.out.println("Problem reading file.");
            System.err.println("IOException: " + e.getMessage());
        }
    }

    /**
     * Determines a colony size
     * pre: none
     * post: All colony cells adjoining and including cell (Row, Col) have 
     * been changed to NON_COLONY, and count of these cells is returned.
     */
    private int collectCells(int row, int col , char colour) {

        if ((row < 0) || (row >= slideData.length) || (col < 0) || (col >= slideData[0].length) || (slideData[row][col] != colour)) {
            return(0);
        } else {
            slideData[row][col] = NON_COLONY;
            return(1 + 
                collectCells(row + 1, col , colour) + 
                collectCells(row - 1, col , colour) + 
                collectCells(row, col + 1 , colour) + 
                collectCells(row, col - 1 , colour) + 
                collectCells(row - 1 , col - 1 , colour) + 
                collectCells(row + 1 , col + 1 , colour) + 
                collectCells(row - 1 , col + 1 , colour) + 
                collectCells(row + 1 , col - 1 , colour));
        }
    }

    /**
     * Analyzes a slide for colonies and displays colony data
     * pre: none
     * post: Colony data has been displayed.
     */
    public void displayColonies() {
        int count;
        System.out.format("%-10s %-10s %-10s" , "LOCATION" , "SIZE" , "COLOUR");
        System.out.println();

        for (int row = 0; row < slideData.length; row++) {
            for (int col = 0; col < slideData[0].length; col++) {
                for (int i = 1; i <= 9; i++) {
                    if (slideData[row][col] == i) {
                        count = collectCells(row , col , (char)i);
                        System.out.format("%-10s %-10s %-10s" , "(" + row + "," + col + ")" , count , i);
                    }
                }
            }
        }
    }


    /**
     * Displays a slide.
     * pre: none
     * post: Slide data has been displayed.
     */
    public void displaySlide() {

        for (int row = 0; row < slideData.length; row++) {
            for (int col = 0; col < slideData[0].length; col++) {
                System.out.print(slideData[row][col]);
            }
            System.out.println();
        }
    }
}

Answer 1

您正在将int（i中的值）（例如3）与字符（例如'1'，'2'...）（slideData中的值）进行比较，这些字符是整数是从0x30（'0'）开始的值。

因此，无需重写程序，最简单的解决方案就是通过将for循环值（1..9）转换为等效的字符来修复不兼容的类型，如下所示：

for (int i = 1; i <= 9; i++)
{
    char x = (char) (0x30 + i);
    if (slideData[row][col] == x)
    {
       // ...
    }
}

要将整数（数字）转换为char，您还可以执行以下操作：

  char x = Character.forDigit(i, 10);

Answer 2

正如其他人也指出的那样-您正在将char（字符）与int（整数）进行比较。当您看到数组slideData中单元格[0] [0]（行= 0和col = 0）的值包含1时，我可能会有些困惑1，但条件失败。但是i数组中存储的内容和整数变量的值之间是有区别的。

在Java中，当您将characters与character进行比较时，JVM将使用字符的ASCII值。这表示值1！='1'，因为ASCII值'1'为49。

由于IDE的调试器如何显示字符数组的值，您可能看不到差异。例如，在IntelliJ中，您将看到： ![slideData[0][0] value and ASCII value] 1 它显示integer中的值为'1'（字符值），其ASCII（整数）值为49。如果您对其进行较小的更改，您的条件将起作用：

slideData[0][0]

整数值48是'0'字符的ASCII值，在其上加上if (slideData[row][col] == 48 + i) { count = collectCells(row , col , (char)i); System.out.format("%-10s %-10s %-10s" , "(" + row + "," + col + ")" , count , i); }的值将得到要比较的字符的ASCII值。

为什么我的数组不能满足此if语句的条件？

2 个答案: