package java_algo_book;

public class AddNumber {

public static class NumberMustBePositive extends RuntimeException {}

// 1 .. untilNumber 까지 값을 더 함

public static int addNumber(int untilNumber) {

if (untilNumber < 0) throw new NumberMustBePositive();

int addNum = 0;

for (int i = 1; i <= untilNumber; i++) {

addNum += i;

}

return addNum;

}

public static int addNumberWhileLoop(int untilNumber) {

if (untilNumber < 0) throw new NumberMustBePositive();

int i = 1;

int sum = 0;

while (i <= untilNumber) {

sum += i;

i++;

}

System.out.println("I index : " + i);

return sum;

}

public static int gausNumber(final int UNTIL_NUMBER) {

final int START_NUMBER = 1;

if (isEvenNumber(UNTIL_NUMBER)) {

return (START_NUMBER + UNTIL_NUMBER) * (UNTIL_NUMBER / 2);

} else {

final int MULTI_NUMBER = UNTIL_NUMBER / 2;

return ((START_NUMBER + UNTIL_NUMBER) * MULTI_NUMBER) + ((START_NUMBER + UNTIL_NUMBER) / 2);

}

}

private static boolean isEvenNumber(int number) {

return number % 2 == 0;

}

public static void main(String[] args) {

int sumNumber = addNumberWhileLoop(5);

System.out.println("Total Sum Number : " + sumNumber);

System.out.print("A");

System.out.println("B");

int num1 = gausNumber(10);

int num2 = gausNumber(13);

System.out.println(num1);

System.out.println(num2);

}

}