Help - (Sorting characters in a string)

[DanPe]

Hi all, first of all I would like to thank you for all the help :) hopefully someday soon I'll be able to help people here as well.
I need to write a program doing this:
(Sorting characters in a string) Write a method that returns a sorted string using the following header:
public static String sort(String s) For example, sort("acb") returns abc.
Write a test program that prompts the user to enter a string and displays the sorted string.

Here's the code I wrote and I have a questions: (don't mind the class name)

import java.util.Scanner;
public class copy {
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		System.out.println("Please enter a string");
		String str = input.next();
		System.out.println("The sorted string is: " + sort(str));
	}
	
	public static String sort (String str)
	{
		StringBuilder newStr = new StringBuilder(str); //create a String Builder
		
		for (int i = 0; i < newStr.length(); i++)
		{
			if (Character.isLetter(newStr.charAt(i))) //if is letter then check which is bigger
			{
			
			}
		}	
		
		for (int i = 0; i < newStr.length(); i++) //eliminate != letters
		{
			if (Character.isLetter(newStr.charAt(i)) == false)
			{
				newStr.deleteCharAt(i);
				i--;
			}
			
		} //end of eliminate != letters
		
		str = newStr.toString(); //convert StringBuilder to String
		return str;
	}
}

I can't figure out how to do the part of sorting the letters...

for (int i = 0; i < newStr.length(); i++)
		{
			if (Character.isLetter(newStr.charAt(i))) //if is letter then check which is bigger
			{
			
			}
		}

Would love to get some help :)

Cheers,
Dan

[j2me64]

read all characters into an array of char and than use Arrays.sort(yourCharArray)