s1.charAt(x)=='a'

public class hhh{
public static void main(String[]args)
 {
   String s1="hkdhskhegoihwhonfdsaaa";
    int count=0;
   
 for(int x=0;x<s1.length();x++)  {
 
  if('a'==s1.charAt(x))                  count++;
    }
   
System.out.println(count);
}
}