# Identify all prime numbers between 100 and 200

Alexander Skagerling

Greenhorn

Posts: 3

posted 12 years ago

Hello everyone!

I'm new user to the Java and I don't understand how to solve this:

What is the code for creating a program which isentify and output all primenumbers between 100 and 200?

Can anyone please help me?

I'm new user to the Java and I don't understand how to solve this:

What is the code for creating a program which isentify and output all primenumbers between 100 and 200?

Can anyone please help me?

Jeroen Wenting

Ranch Hand

Posts: 5093

posted 12 years ago

a prime is a number that yields an integer value when divided by any number other than itself (and 1).

In practice the test does not have to be run for numbers greater than the square root of the number being tested rounded up to the next whole number.

Also, only other prime numbers need to be taken into consideration (whether applying that is cheaper than a brute force approach is open for debate and implementation dependant).

As a result of the rules, you only need to test odd numbers and need to divide only by odd (prime) numbers smaller than the square root of the candidate prime under consideration.

By taking an array of odd numbers between 100 and 200 and iterating over that building an array of primes found you will get what you want.

In practice the test does not have to be run for numbers greater than the square root of the number being tested rounded up to the next whole number.

Also, only other prime numbers need to be taken into consideration (whether applying that is cheaper than a brute force approach is open for debate and implementation dependant).

As a result of the rules, you only need to test odd numbers and need to divide only by odd (prime) numbers smaller than the square root of the candidate prime under consideration.

By taking an array of odd numbers between 100 and 200 and iterating over that building an array of primes found you will get what you want.

42

John Smith

Ranch Hand

Posts: 2937

posted 12 years ago

Are you in the same class with Linnea Palin? She already asked exactly same question here. The answer is, of course, that no one will do your homework for you, but we are willing to help you if you hit a wall.

**What is the code for creating a program which isentify and output all primenumbers between 100 and 200?**

Are you in the same class with Linnea Palin? She already asked exactly same question here. The answer is, of course, that no one will do your homework for you, but we are willing to help you if you hit a wall.

Jeroen Wenting

Ranch Hand

Posts: 5093

Alexander Skagerling

Greenhorn

Posts: 3

Alexander Skagerling

Greenhorn

Posts: 3

posted 12 years ago

Can you maybe give some examples of books, or site which canngive me the code for free? =)

Originally posted by Jeroen Wenting:

It's a pretty standard assignment

That's why I give just the math behind it in words, let them figure it out for themselves (or slavishly copy it from any of a thousand books of course and hope their instructor hasn't read the same book).

Can you maybe give some examples of books, or site which canngive me the code for free? =)

posted 12 years ago

Sure. here is a web page which would be very helpful to you. Be sure to read the whole thing!