occurence of char in a string

[suman deb]

hi all,

how to find out the occurence of each char in a string? e.g.

for the string "HELLO" , the required out put is--

H - 1
E - 1
L - 2
o - 1

please help

[Christophe Verré]

You could try with String.indexOf(int ch, int fromIndex), looping through the whole String.

[Allan Morris]

Hi, a map is a good data structure, pairing each character to a count. You can do it like this using the Collections framework:

import java.util.*;
 
/*Count the occurences of characters in a string.
 **/
 
public class QuickTest
{
private static String data = "Hello";
 
public static void main(String[] args)
{
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
char[] tempData = data.toCharArray();

//Count the characters
for(char current : tempData)
{
if(map.containsKey(current))
{
map.put(current, map.get(current)+1);
}
else
map.put(current, 1);
}

/** Output results,
  * It's necessary to create a set view because maps don't provide an iterator
  */ 
Set<Map.Entry<Character, Integer>> results = map.entrySet();
for(Map.Entry<Character, Integer> entry : results)
{
System.out.print(entry.getKey() + " - ");
System.out.println(entry.getValue());
}
}
}

[ September 05, 2006: Message edited by: Allan Morris ]