Minimum Sum

This program finds the minimum n where the sum of 1+2+..+n > 1000. This exercise helps users understand while loop. It also illustrates the use of a main method.

Download files: MiniSum.java
Areas: main

MiniSum.java

1	/**This program finds the minimum n where the sum of 1+2+..+n > 1000.
2	*/
3
4	import java.io.*;
5	import java.lang.System.* ;
6
7	public class MiniSum {
8
9	final static int UPPERLIMIT = 1000;
10	private static int sum = 0;

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Question 1

Is it necessary for the program to import java.lang.System.*? Can we delete the import statement?

Question 2

Can other classes have access to sum which is defined in private static int sum = 0; ?

Question 3

What is the difference between n++ and ++n?

Question 4

Describe what sum += n++; does? How does it change the values of sum and n?

Question 5

In the end of the method findMinimum, why return n-1 rather than n?

Question 6

What is the difference between the print and println method?

Question 7

Which is the entry point for running an application, findMinimum or main method?

Question 8

Suppose we change the requirement of the program. We replace 1000 with 6. That is, we want to find the minimum n where 1+2+..+n > 6. If we only replace line 9 of the code:
final static int UPPERLIMIT = 1000;
with
final static int UPPERLIMIT = 6;
would the program work?

Question 9

With reference to the previous question, how should we change the program to satisfy the modified requirement?

Question 10

Suppose we make the change suggested in the solution of the previous question, but we do not change line 9. That is UPPERLIMIT is 1000. Would the program satisfy the original requirement?