Java program to calculate the number of times each character appears in a string

Question

I typed out this program to count the number of times each character appears in a String.

  import java.util.Scanner;
  public class fre {


public static void main(String[] args) {
    Scanner s=new Scanner (System.in);
    System.out.println("Enter a string");
    String sent = s.nextLine();
    String str=sent.toUpperCase();
    int len=str.length();
    char save[]=new char[len];
    for (int i=0;i<len;i++){

        save[i]=str.charAt(i);


    }
    char a=0;
    int count=0;
    for(int i=0;i<len;i++){

        a=save[i];
        for(int j=0;j<len;j++){
            if(save[j]==a)
                count ++;
            }

            }
    for(int i=0;i<len;i++)
    System.out.println(save[i]+" appears "+count+" number of times");
}

}

The code is horribly wrong, can someone please guide me as to how to go about the program using simple functions and tell me what I've done wrong here?

For what it's worth, if you want to get an array of `char`s from a `String`, no need to do the loop yourself; there's already a `toCharArray` method. — Dennis Meng, Jan 16 '14 at 19:19

score 2 · Answer 1 · answered Jan 16 '14 at 17:10

2

You can do it simply by

Declaring an array of 26 integers (1st index refers to A, second to B and so on)
Just traverse the input string once and for each character you traverse in string, increment corresponding index, you can do it simply like int index=inputString[i]-65; and increment this index.
Now traverse your array for the counts of each character and you are done, Hope it helps

answered Jan 16 '14 at 17:10

Ahmed

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I'm assuming that your string only contain english alphabets – Ahmed Jan 16 '14 at 17:13

score 1 · Answer 2 · answered Jan 16 '14 at 17:10

1

How about

  int[] count = new int[256];
  for(int ch; (ch = System.in.read()) >= ' ';)
      count[ch]++;
  for(char ch = 0; ch < count.length; ch++)
      if (count[ch] > 0)
          System.out.println(ch + " appears " + count[ch] + " times");

answered Jan 16 '14 at 17:10

Peter Lawrey

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Jean Logeart · Answer 3 · 2014-01-16T17:13:48.327

0

You have one global count while you need one counter for each character.

Try using a Map<Character, Integer> to store the number of occurences of each character in your string.

edited Jan 16 '14 at 17:13

answered Jan 16 '14 at 17:08

Jean Logeart

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score 0 · Answer 4 · answered Jan 16 '14 at 17:09

0

You need a separate count for each character. Right now you are incrementing the same count.

answered Jan 16 '14 at 17:09

Dodd10x

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score 0 · Answer 5 · answered Jan 16 '14 at 17:25

0

If i understand what you want is something like this:

    int count = StringUtils.countMatches("Auto-generated method stub", "e");
    System.out.println(count);

StringUtils is a api from apache http://commons.apache.org/proper/commons-lang/

answered Jan 16 '14 at 17:25

xild

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score 0 · Answer 6 · answered Jan 16 '14 at 17:43

You can also use Collections.frequency(Collection<?> c, Object o) method to get count of an element in a collection, So below code snippet will give you the character count in a string.

String str=s.nextLine().toUpperCase();
         char[] letters=str.toCharArray();
         List<Character> cList = new ArrayList<Character>();
         for(char c : letters) {
             cList.add(c);
         }
         Set<Character> chSet=new HashSet<Character>(cList); //to get unique characters in the list
         for(Character ch:chSet) {
             System.out.println(ch+"          "+Collections.frequency(cList, ch));
         }

Java program to calculate the number of times each character appears in a string

6 Answers6