# Returning if a number is prime. (Chapter on Objects and classes. OOP)

Allen Hsia
Greenhorn
Posts: 20
Ok i search and im' sure there i couldn't find something like this.

Design a class named MyInteger. The class contains:
**An int data field named value taht stores the int value represented by thsi object.
**a constructor that creates a MyInteger object for the specified int value
**A get method that returns the int value.
**Methods isEven(), isOdd(), and isPrime() that return true if the value is even, odd, or prime, repectively.
**Static methods iEven(int), isOdd(int), and isPrime(int) taht return true if the specified value is even, odd, or prime, respectively.
**Static methods isEven(MyInteger), isOdd(MyInteger), and isPrime(MyInteger) that return true if the specified value is even, odd, or prime, respectively.
**Methods equals(int) and equals(MyInteger) taht return true if the value in the object is equal to the specified value.
** a static method parseInt(char[]) that converts an array of numeric characters to an int value.

draw the UML diagram for the class. implement the class. Write a cleint program taht tests all methods in the class.

I"m at the returning Prime if the number is prime.
How do i prove it's prime? I know how to prove if it's even or odd but prime is only divisible by one and itself.

Janeice DelVecchio
Saloon Keeper
Posts: 1809
12
I just did one of these.... I used this as my outline for the algorithm....

http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

Hope that helps.

Lee Kian Giap
Ranch Hand
Posts: 213

http://en.wikipedia.org/wiki/List_of_prime_numbers

http://www.mathforum.org/dr.math/faq/faq.prime.num.html

Hunter McMillen
Ranch Hand
Posts: 492
Hi,

Janeice's idea of using the Sieve of Eratosthenes will work really well but you could always use loops as well. And search for all possible factors of a number.

-Hunter

Greenhorn
Posts: 9
To check if number n is prime or not,see if it is divisible by numbers ranging from 2 to n/2.If it is divisible then it is not prime.

Campbell Ritchie
Sheriff
Posts: 50168
79
Your isEven() method does not even slightly fulfill your requirements. I don't think it will compile. Ditto isOdd().

Please don't anybody give any more hints, otherwise you will overstep the line between helping and doing somebody else's assignment.

You are not going about things correctly. You should not be creating a whole class. You should create a little class with an isEven method only, execute and test that, then add an isOdd method, and so on. You will find it much easier if you develop in tiny bits.

Draw your UML diagrams first. They can easily be drawn from the specification you are given and you can pick up 10% of your marks in 20 minutes.