在java中计算特定字符，但我的程序只读取单词中的第一个字符

Question

我有一个程序，可以计算指定文件中特定字符（如“a”）的所有实例。我让它数一数字符，除了它只看单词开头的字符。所以“aaba”只能算作4个“a”，而不是7个。我已经尽我所能地发表了评论，所以我的思路很清晰，但我对编程相当陌生，所以如果我不清楚，我提前道歉

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

public class Charcounter
{
public static void main(String[] args) throws IOException
{
    //accumulator
    int sum = 0;

    Scanner kb = new Scanner(System.in);

    //get filename and character to be counted from user
    System.out.println("Enter the name of a file: ");
    String filename = kb.nextLine();
    System.out.println("Enter the name of the character to be counted: ");
    char countedChar = kb.next().charAt(0);

    //check if file exists
    File file = new File(filename);
    if (!file.exists())
    {
        System.out.println("File specified not found.");
        System.exit(0);
    }

    //open file for reading
    Scanner inputFile = new Scanner(file);

    //read file and count number of specified characters
    while (inputFile.hasNext())
    {
        //read a char from the file
        char count = inputFile.next().charAt(0);

        //count the char if it is the one specified
        if (count == countedChar)
        {
             ++sum;
        }

    }

    //close file
    inputFile.close();

    //display number of the specified char
    System.out.println("The number of the character '" + countedChar + "' is : " + sum);
}
}

Answer 1

这是因为你只是在比较第一个角色

 //read a char from the file
 // THIS : only the first character
 char count = inputFile.next().charAt(0);

 //count the char if it is the one specified
 if (count == countedChar)
 {
   ++sum;
 }

您应该循环遍历所有字符，然后如果与countedChar匹配，则增加总和，类似

 String str = inputFile.next()
 for (int i = 0; i < str.length(); i++) {
   char count = str.charAt(i);   
   // check if it matches the countedChar and then increment.
 }

Answer 2

尝试使用一个变量，而不是在类的开头初始化为零的零，然后对它计数的每个字符递增，因此：

   //read a char from the file
    char count = inputFile.next().charAt(m);
    ++m;
    //count the char if it is the one specified
    if (count == countedChar)
    {
         ++sum;
    }

然后在主要方法中定义：

   int m = 0

Answer 3

那是因为你只是在读第一个字符

    String word = inputFile.next();     //read a word
    int counter = 0; 

    for(counter=0;counter<word.length();counter++) // traverse through the word
    { 
        char count = word.charAt(i);       // ith char

        //count the char if it is the one specified
        if (count == countedChar)
        {
             ++sum;
        }
   }

Answer 4

作为替代方案，您可以使用专用于字符读取的读卡器：

BufferedReader reader = new BufferedReader(new FileReader(file));

int read;

while((read = reader.read())>0) if (read==countedChar) count++;

reader.close();

Answer 5

while (inputFile.hasNext()) {
    String word = inputFile.next();
    for (int i = 0; i < word.length(); i++) {
        if (word.charAt(i) == countedChar) {
            ++sum;
        }
    }
}

Answer 6

这是因为你正在使用

char count = inputFile.next().charAt(0);

默认情况下next将一直读取，直到找到空白或数据结尾，所以现在它读取并返回整个单词

如果你想让这种方法起作用，你需要next一次只返回一个字符，所以在imputFile扫描器中设置分隔符为空字符串，比如inputFile.useDelimiter("");