// Marty Stepp, CSE 142, Autumn 2008
// This file contains several logical methods we wrote in class to practice
// for the midterm.  You can test the output of methods like these on our
// Practice-It system on the course web site.

import java.util.*;   // for Scanner, Random

public class LogicMethods {
	public static void main(String[] args) {
		System.out.println("digit sum of 29107: " + digitSum(29107));
		System.out.println();
		
		System.out.println("is vowel Q: " + isVowel("Q"));
		System.out.println("is vowel a: " + isVowel("a"));
		System.out.println("is vowel E: " + isVowel("E"));
		System.out.println("is vowel x: " + isVowel("x"));
		System.out.println("is vowel McCain: " + isVowel("McCain"));
		System.out.println();
		
		System.out.println("is all vowels eIEiO: " + isAllVowels("eIEiO"));
		System.out.println("is all vowels oink: " + isAllVowels("oink"));
		System.out.println("is all vowels Obama: " + isAllVowels("Obama"));
		System.out.println("is all vowels AOi: " + isAllVowels("AOi"));
	}
	
	// Returns the sum of the digits of the given integer.
	// For example, digitSum(29107) returns 2+9+1+0+7 or 19.
	public static int digitSum(int n) {
		n = Math.abs(n);         // for negative numbers
		
		// compute cumulative sum of digits
		int sum = 0;
		while (n != 0) {
			int digit = n % 10;   // 7
			n = n / 10;           // 2910
			sum = sum + digit;
		}
		
		return sum;
	}
	
	// Returns true if every character of the given String is a vowel (aeiou).
	// Returns false if any character is a non-vowel.
	public static boolean isAllVowels(String s) {
		for (int i = 0; i < s.length(); i++) {
			// charAt
			String letter = s.substring(i, i+1);
			if (!isVowel(letter)) {
				return false;
			}
		}
		return true;
	}
	
	// Returns true if the given String is a vowel (aeiou, case-insensitive).
	// Returns false for all other Strings.
	public static boolean isVowel(String s) {
		s = s.toLowerCase();
		
		// "Boolean Zen" - we can directly return the result of a logical test
		return (s.equals("a") || s.equals("e") || s.equals("i") ||
				s.equals("o") || s.equals("u"));

		/*
		// longer version - also works but not as zen-like
		if (s.equals("a") || s.equals("e") || s.equals("i") ||
				s.equals("o") || s.equals("u")) {
			return true;
		} else {
			return false;
		}
		*/
	}
}