How to convert for loop to do-while loop?

Question

This is a question from the book Introduction to Java by Y Daniel Liang:

Convert for loop statement to a while loop and do-while loop?

 int sum = 0; for (int i = 0; i <= 7; i++) sum = sum + i;

I am pretty confused on how to convert it to a do-while loop. What am I supposed to do? Please see my code below.

public class Convert_forLoop_toWhileLoop {
    
   public static void main(String[] args) {
       int sum = 0;
       int i = 0;
       do {
           sum = sum + i;
           System.out.println(sum);
           i++;
       } while(i <= 7); 
    }
}

Answer 1

Depending on how scrupulous you wanna be, a "more" equivalent do - while -loop of your for -loop example would be:

int sum1(int n) {
    int sum = 0;
    for (int i = 0; i <= n; i++) {
        sum = sum + i;
    }
    return sum;
}

int sum2(int n) {
    int sum = 0; 
    {
        int i = 0;
        if (i <= n) {
            do {
                sum = sum + i;
                i++;
            } while (i <= n);
        }
    }
    return sum;
}

Note I wrapped your example in sum1 (passing sum1(7) is equivalent to your case).

For those who really want to split hairs -- note Java doesn't necessarily compile the 2 functions above into the same bytecode (at least when I tested it, to my surprise). 2 extra bytecode instructions for sum2 (20 vs. 22). Just something interesting I noticed.

Answer 2

Like this:

int sum = 0;
int i = 0;

do {
   sum += i;
   i++;
} while (i <= 7);

System.out.println("The sum of 0 thru " +i + " is:" + sum);

Answer 3

Your answer doesnt support the case where i initial value is >= number of loops.

you need to first check the condition.

while (i <= 7) {
    sum+=i;
   // at the last statement increase i
   i++
}

System.out.println(sum);