Efficient way to find Frequency of a character in a String in java : O(n)

Question

In a recent interview I was asked to write the below program. Find out the character whose frequency is minimum in the given String ? So I tried by iterating through the string

Answer 1

The process of finding frequency of characters in a String is very easy.
For answer see my code.

import java.io.*;
public class frequency_of_char
{
    public static void main(String args[])throws IOException
    {
        BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
        int ci,i,j,k,l;l=0;
        String str,str1;
        char c,ch;
        System.out.println("Enter your String");
        str=in.readLine();
        i=str.length();
        for(c='A';c<='z';c++)
        {
            k=0;
            for(j=0;j0)
            System.out.println("The character "+c+" has occured for "+k+" times");
        }
    }
}