Question

A perfect number is a positive integer that is equal to the sum of its (proper) positive divisors, including 1 but excluding itself. A divisor of a number is one which divides the number evenly (i.e., without a remainder).

For example, consider number 6. Its divisors are 1, 2, 3, and 6. Since we do not include number itself, we only have 1, 2, and 3. Because the sum of these divisors of 6 is 6, i.e., 1 + 2 + 3 = 6, the number 6 is a perfect number.

Write a Java program that reads in an integer value from the user (say val) and outputs whether this entered number is a perfect number or not. Your program should prompt and print the output as shown in examples below. First example,

Enter an integer: 6
6 is a perfect number!

Second example,

Enter an integer: 8
8 is NOT a perfect number.

Values shown in bold font in above examples are user entered values.

Hint: Steps of this program can be summarized as follows:

1) Read in the user input and store it using an integer variable (say val). (You can assume that user passed in value will be at least 2.)

2) Declare an integer variable (say divisorSum) to store the sum of the divisors. Initialize it to one.

3) User for loop as,

for(int i=2; i<val; i++)
{
 /*
  If i is a divisor of val, then update divisorSum
  such that divisorSum is assigned to the sum of 
  divisorSum (from the previous iteration) and i.
 */
}

4) If divisorSum equals to val, then display "val is a perfect number!", otherwise, display "val is NOT a perfect number"

Answer 1

`Hey,

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import java.util.Scanner;

/**
* @author
*
*/
public class PerfectNumber {

/**
* @param args
*/
public static void main(String[] args) {

Scanner scanner = null;
try {

scanner = new Scanner(System.in);
// prompt to read the number
System.out.print("Enter an Integer: ");
int val = scanner.nextInt();
int divisorsSum = 1;

// repeat the loop to get sum of the divisors
for (int i = 2; i < val; i++) {

if (val % i == 0)
divisorsSum += i;
}

// check with val and sum of divisors
if (divisorsSum == val) {
System.out.println(val + " is a perfect number");

} else {

System.out.println(val + " is not a perfect number");
}

} catch (Exception e) {
// TODO: handle exception
}
}
}

Kindly revert for any queries

Thanks.