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

Allen Hsia
Greenhorn

Joined: Oct 29, 2009
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

Joined: Sep 14, 2009
Posts: 1660
    
  11

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.


When you do things right, people won't be sure you've done anything at all.
Lee Kian Giap
Ranch Hand

Joined: Jan 23, 2008
Posts: 213
google "what is prime number"

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

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


SCJP 6, SCWCD 5, SCBCD 5
Hunter McMillen
Ranch Hand

Joined: Mar 13, 2009
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


"If the facts don't fit the theory, get new facts" --Albert Einstein
Adithya Bhat
Greenhorn

Joined: Nov 06, 2009
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

Joined: Oct 13, 2005
Posts: 38353
    
  23
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.
 
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