TCHS-7-250

Problem Statement
	You are given a String text. Determine the letters (both lowercase and uppercase) that appear in text. Return a String which contains those letters, converted to lowercase, and then sorted in alphabetical order. The returned String should include all occurrences of each letter.
Definition
	Class: TextProcessor Method: collectLetters Parameters: String Returns: String Method signature: String collectLetters(String text) (be sure your method is public)
Constraints
-	text will contain between 1 and 50 characters, inclusive.
-	text will contain only letters ('A'-'Z', 'a'-'z'), digits ('0'-'9'), and spaces (' ').
Examples
0)
	"She sells sea shells" Returns: "aeeeehhllllssssss" The letters that appear in the input are "shesellsseashells" (converted to lower case and ignoring non-letter characters). Then we sort these letters alphabetically.
1)
	"ReMemBEr To IgnoRE CASe" Returns: "abceeeeegimmnoorrrst"
2)
	"12345" Returns: "" There are no letters, so the empty String should be returned.
3)
	"TopCoder is fun" Returns: "cdefinooprstu"
4)
	"Knights are better than Bishops" Returns: "aabbeeeghhhiiknnoprrssstttt"

import java.util.*;

public class TextProcessor {

	public static String collectLetters(String text) {
		List<Character> list = new ArrayList<Character>();
		for (int i = 0; i < text.length(); i++) {
			char ch = text.charAt(i);
			if (Character.isLetter(ch)) {
				if (Character.isUpperCase(ch))
					ch = (char) (ch - 'A' + 'a');
				list.add(ch);
			}
		}
		Collections.sort(list);
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < list.size(); i++)
			sb.append(list.get(i));
		return sb.toString();
	}

}