How do I fix a String type isn't applicable for argument boolean in my method?

Question

I am extremely new to coding and learning it in my school currently. My teacher assigned us to write a method that would take a string and return it looking as a triangle, for example if dog was entered it would return:

ddd oo g all on separate lines.

What I have so far is below, I keep getting an error when trying to use substring in the method saying the string type isn't applicable here. Can someone help me?

String go( String a) 
{
  int count = 0;
  for(int i = a.length(); i<=0; i--)
  {
    While(a.substring(count<=i));
    {
      System.out.println(a.substring(count,count+1));
      count++;
    }
    
  }
}

Answer 1

The keyword is while , not While .

It needs a boolean condition, while a.substring(…) looks as if you want to pass a string instead. That's probably not your intent: You already have a boolean condition there: count <= i , which should be the sole argument for the while loop.

Answer 2

This is how you wannna write your while loop:

while(count <= i){
  System.out.println(a.substring(count,count+1));
  count++;
}

Answer 3

It's while and not While . I suggest another solution with two for loops.

   public String go(String a) {
   int l=a.length();
   String ch="";
   for (int i=0;i<l;i++) {
       for (int j=0;j<l-i;j++) 
         ch = ch + a.charAt(i);
   }
   return ch;
 }