Exercise SumAndAverage (Loop) ~ Programming is Fun
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Saturday, September 6, 2014

Exercise SumAndAverage (Loop)

Write a program called SumAndAverage to produce the sum of 1, 2, 3, ..., to an upperbound (e.g., 100). Also compute and display the average. The output shall look like:
The sum is 5050
The average is 50.5
Hints:
public class SumAndAverage {   // saved as "SumAndAverage.java"
   public static void main (String[] args) {
      int sum = 0;          // store the accumulated sum, init to 0
      double average;       // average in double
      int lowerbound = 1;   // the lower bound to sum
      int upperbound = 100; // the upper bound to sum

      for (int number = lowerbound; number <= upperbound; ++number) { // for loop
         sum += number;     // same as "sum = sum + number"
      }
      // Compute average in double. Beware that int/int produces int.
      ......
      // Print sum and average.
      ......
   }
}
TRY:
  1. Modify the program to use a "while-do" loop instead of "for" loop.
    int number = lowerbound;
    int sum = 0;
    while (number <= upperbound) {
       sum += number;
       ++number;
    }
  2. Modify the program to use a "do-while" loop.
    int number = lowerbound;
    int sum = 0;
    do {
       sum += number;
       ++number;
    } while (number <= upperbound);
  3. What is the difference between "for" and "while-do" loops? What is the difference between "while-do" and "do-while" loops?
  4. Modify the program to sum from 111 to 8899, and compute the average. Introduce an int variable called count to count the numbers in the specified range.
    int count = 0;   // count the number within the range, init to 0
    for (...; ...; ...) {
       ......
       ++count;
    }
  5. Modify the program to sum only the odd numbers from 1 to 100, and compute the average. (Hint: n is an odd number if n % 2 is not 0.)
  6. Modify the program to sum those numbers from 1 to 100 that is divisible by 7, and compute the average.
  7. Modify the program to find the "sum of the squares" of all the numbers from 1 to 100, i.e. 1*1 + 2*2 + 3*3 + ... + 100*100.
Comment your answers :)


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