Java Program to Count Frequency of Each Character in a String

import java.util.Scanner;

class Frequency
{
 public static void main(String...s)
 {
  String str="";
  int count=0,len=0,flag=0;

  Scanner sc=new Scanner(System.in);
  System.out.print("nEnter a string:");
  
  str=sc.nextLine();
  len=str.length();
  
  for(int i=0;i<len;++i)
  {
   count=0;
   for(int j=0;j<len;++j)
    if(str.charAt(j)==str.charAt(i))
     count++;

   for(int k=0;k<i;++k)
    if(str.charAt(k)==str.charAt(i))
     flag=1;

   if(flag!=1)
    System.out.print(str.charAt(i)+":"+count+"n");

   flag=0;
  }
 }
}