Section Handout #4 - 1

Adding Commas to Numeric Strings

import acm.program.*;

public class String_Methods extends ConsoleProgram {
	public void run() {
		while (true) {
			String digits = readLine("Enter a numerical string: ");
			if (digits.length() == 0) break;
			println(addCommasToNumericString(digits));
		}
	}
	
	private String addCommasToNumericString(String digits) {
		int nDigits = digits.length(); // creates integer counting the number of digits
		String delimString = digits; // string delimited by commas, initialised equivalent to digits
		while (nDigits > 3) {
				String afterComma = delimString.substring(nDigits - 3); // substring containing every char after 3rd from last
				// delimString = everything before 3rd from last char + ',' + everything after 3rd from last char
				delimString = digits.substring(0, nDigits - 3) + ',' + afterComma;
				nDigits -= 3; // tells program to discount last 3 digits (as comma has now been added)
		}
		return delimString;
	}
}