Counting one character at a time from a file

[G. Graz]

I am trying to count and store the frequency each letter occurs form a .txt file . I am at the point where I can read back the file but I can not get any methods to work that would count the frequency of a letter in that file .

   

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
import javax.swing.JOptionPane;

public class nCount {

    public static void main(String[] args) throws IOException {

 nCount ri = new nCount();
 ri.doIt();
 
 }

 private void doIt()
 {
 try{

 char[] letters = new char[250];

 String ans;
 ans = JOptionPane.showInputDialog(null, "Please enter in the location of your file ");
 BufferedReader br = new BufferedReader(new FileReader(ans));
 Scanner sc = new Scanner(br).useDelimiter(" ");

 br.read(letters);

 for (int i = 0; i < letters.length; i++)
 {
 
 char c = letters[i];
 String d = Character.toString(c).toLowerCase(); 
 System.out.print(d);
 }

 } 
}

Simple ..no problems but here is some code that I think works in regard to counting the frequency but I am missing something to get it to function correctly ? Any ideas please let me know ! Thank you .

  
 
int count = 0;
 for (int ch = br.read(); ch >=0; ch = br.read()){
     switch (ch){
         case'a':case'A':
             count ++;
     }

 }
   System.out.println(count);

 }
  

Again something where I think it would work but just do not see the error ?

 

int[] count = new int[26];

 // Get contents from the text area
     String text = sc.toString();

     text = text.toUpperCase();

     // Count occurrence of each letter (case insensitive)
       for (int i = 0; i < text.length(); i++)
        {
          char character = text.charAt(i);

          if ((character >= 'A') && (character <= 'Z'))
          {
            count[(int)character - 65]++; // The ASCII for 'A' is 65
          }
          }
          return count; // Return the count array
   

So basically , I need to read a .txt file and print out that the character 'A' appeared x number of times .

Thank you again !

[Rob Spoor]

G. Graz wrote:

br.read(letters);
for (int i = 0; i < letters.length; i++)

That's a bad idea. The read method returns how many characters were actually read; it can be anywhere between 0 and letters.length. If it is less than letters.length, the remainder will contain the characters that were already in the array before the call to read (in this case '\0'). You'd better use the return of br.read(letters).

As for your problem, usually when counting occurrences a Map is used:

Map<Character,Integer> characterCounts = new HashMap<Character,Integer>();

Integer count = characterCounts.get(ch); // autoboxing
if (count == null)
{
    characterCounts.put(ch, 1);
}
else
{
    characterCounts.put(ch, count + 1);
}

[Ulf Dittmer]

The standard idiom would be a loop like this:

int read;
while ((read = br.read()) > 0) {
	...
}

Just to confuse you :-) , note that counting characters gets harder if the text can contain the full range of Unicode characters.