Counting the number of characters in a string for beginners in java

topic:

Given a string str = "yekmaakkccekymbvb". Count the number of characters in the string and print out the number of each character. 

Ideas:

Replace the first character of the string with [""], and then calculate the difference with the string before substitution, and the difference obtained is the number of the first character. 

Code:

public class CharTypeStat{
	public static void main(String[] args){
		String str = "yekmaakkccekymbvb";
                int i = 0;//Count the number of characters
		while(!"".equals(str)){
			String s = str.substring(0, 1);//Get the number of characters to be counted
			String tmp = str.replace(s, "");//Replace with empty
			System.out.println(String.format("Character %s has %2d.", s, str.length()-tmp.length()));
			str = tmp;//Get the string that has not yet been counted
		}
                System.out.println("According to statistics, there are "+i+" characters in this string.");
	}
}