Help me getting prime numbers

hi,
can anyone help me with this i'm newbie and can't figure the solution out
"Write a multithreaded Java program that outputs prime numbers.
This program should work as follows: The user will run the program
and will enter a number on the command line The program will then
create a separate thread that outputs all the prime numbers less than or
equal to the number that the user entered".
thx in advance

prime numbers are numbers that can only be divided by 1 and itself
1,2,3,5,7,9,11,...
maybe the only condition u can check is whether it is divideable by 2 , 3 or 5 but you have to exclude 2 ,3 and 5
since all numbers (except prime numbers) are made up from multiplication from 2, 3 ,and 5, you can use that logic
example :
4 <-- divideable by 2 <-- not prime
9 <-- divideable by 3 <-- not prime
23 <-- not divideable by 2 , 3 , or 5 <-- then it is prime
if(nums == 2 || nums == 3 || nums == 5)
     //it is prime for sure
else if(nums % 2 == 0 || nums % 3 == 0 || nums % 5 == 0)
     //it is not prime
else
   // it is prime number

Similar Messages

Need help with finding prime numbers

I have seen this question asked several times so i apologize for asking once again but I am very new to programming and could use some help. I know the way I have the extra if statements is not at all efficient but I cannot seem to figure out how to get a nested for statement with a divisor to work. The error I'm getting with this current code is that the second for statement needs to be boolean.
package primenumbers;
* @author Owner
public class Main {
     * @param args the command line arguments
    public static void main(String[] args) {
        int primecount; //running total of prime numbers
        int incrementer; //increment numbers
        int sqrtInc; //square root of current increment
        int divisor;
        //set variables to 0
        primecount =0;
        incrementer=3;
        sqrtInc = (int)Math.sqrt(incrementer);
        divisor = 0;
     //print 2
        System.out.println("2");
     for(incrementer = 3; incrementer < 10000; incrementer = incrementer + 1 )
                 if (incrementer % 2 != 0)
              if (sqrtInc % 3 != 0)
                 if (sqrtInc % 5 != 0)
                      if (sqrtInc % 7 != 0)
                          if (sqrtInc % 9 != 0)
                              if (sqrtInc % 11 != 0)
    for (divisor = 3; divisor = incrementer; divisor = divisor +1)
                              if ( incrementer % divisor !=0)
              if (incrementer % (Math.sqrt(incrementer)) != 0)
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    }

aeakers wrote:
I thought I had described it. I appreciate the help but it seems pretty clear to me what this program is supposed to do.Yes, what it's supposed to do is clear: It's supposed to find some prime numbers.
What's not clear, and what I'm asking about, is what algorithm you're trying to use. There's more than one way to find primes, and they all start with no regard whatsoever or any programming language. Then they get implemented in a programming language. It's not clear at all from that mess of code what algorithm you're trying to implement.
And especially in the followup posts. Nope. Nothing was clarified there.
Program should list every prime number that is less than 10000.
I have it to check if the modulus is not zero for the following conditions:
-divided by 2
-square root divided by 3
-square root divided by 5
-square root divided by 7
-square root divided by 9
-square root divided by 11Why those particular numbers?
Then check the modulus is not zero for the following
number divided by a second number that increases up to the first numberI think I kind of get what you're saying here, but I don't think you understand it well enough to translate it to Java.
I am really trying to get you the information you need but I am not at all familiar with this.The point here is that programming is as much about clarity and specificity of thought and communication as it is about the mechanics of the language. If you can't clearly and precisely express what you're trying to do--without regard to any programming language--then you won't be able to program it.
At the very least, if you can't find a way to express your algorithm clearly and precisely, then you ought to put print statements in at each step of your program so you can see exactly what's happening each step of the way, compare that to what you think should be happening, and then find out where you're going wrong.
Also, as a point of best practice, you should alaways use braces for if, for, etc., even when they're not strictly necessary.
// bad
if (...)
singleStatement();
// good
if (...) {
singleStatement();
}

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Hi all,
I am very new to java, and I have exhausted all of my resources before posting here. I have checked the archives but what I am looking for is not really there. I have an exam in 2 days, and there is a question like this one I cannot get to work.
I am supposed to ask for two numbers, the startNumber and endNumber. Then I am supposed to print in ascending or ascending order (this is already done)only the numbers divisible by 4 and the prime numbers. I have seen in the archives how you can use a boolean to check for prime numbers, but given the complexity of this question, I cannot put it into practice. Anybody can help me please?
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import java.awt.event.*;
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Hi all,
Iam very new to java, and I have exhausted all of my
resources before posting here. I have checked the
archives but what I am looking for is not really
there. I have an exam in 2 days, and there is a
question like this one I cannot get to work.
I am supposed to ask for two numbers, the startNumber
and endNumber. Then I am supposed to print in
ascending or ascending order (this is already
done)only the numbers divisible by 4 and the prime
numbers. I have seen in the archives how you can use a
boolean to check for prime numbers, but given the
complexity of this question, I cannot put it into
practice. Anybody can help me please?
Code SNIP
I'm sure there are better ways than this but it's the only one I can think of offhand.
Create a boolean array from 2 to the largest number, set them all to true, then go through and on the first true number set all the multiples to false. Then do the same with the next true number(Sieve of Erasthoenes). Then you can go through and set all the mutiples of 4 to true with another loop. Then print the numbers in the range.

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I am beginning computer science major and I am completely lost with this. Can anyone help me figure this out?
Due: Monday, January 14, 10:00 am
Write a program that calculates all prime numbers less than 10,000. The program works as follows:
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brriney wrote:
I am beginning computer science major and I am completely lost with this. Can anyone help me figure this out?
Due: Monday, January 14, 10:00 am This is what I felt like typing in response to your post:
Thank you for posting your assignment and telling us when it is due. Now please sit back, kick your feet up, have some donuts while we work on your homework.
But I won't ;). Let me tell you just this. Dumping the assignment here without showing any work (and giving a deadline no less!) is tantamount to asking the volunteers here to do your assignment and will only get you flamed. We will help those that show some effort; so please please show your work and ask specific questions regarding your code.
Also, when posting your code, please use code tags so that your code will retain its formatting and be readable. To do this, either use the "code" button at the top of the forum Message editor or place the tag [code] at the top of your block of code and the tag [/code] at the bottom, like so:
[code]
// your code block goes here.
[/code]

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HI, im having trouble with my printPrimeNumbers() method printing the current state of an array, I can only get it to print the original state it was in. The array is inside of a primeNumbers object. I used checkAndResize to resize that array. my printPrimeNumbers method must be void without a parameter. How could i get my PrintPrimeNumbers method to print out a resized array without modifying the parameter? Any ideas.
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* Created by IntelliJ IDEA.
* User: Kevin
* Date: Mar 4, 2007
* Time: 1:53:56 AM
* To change this template use File | Settings | File Templates.
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else
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here is the client code
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        System.out.println("There are " + test.getNumberPrimeNumbers(16) +
                " prime nummbers in the sieve from 1 to 15. \n");
        System.out.println("There are " + test.getNumberPrimeNumbers(26) +
                " prime numbers in the resized sieve from 1 to 25.");
        System.out.println("\nThe first 25 prime numbers are:");// makes sense why it doesnt work
        test.printPrimeNumbers();
        System.out.println("\nThe 13th prime number is: " + test.getNthPrime(13));
        System.out.println();
        System.out.println("The number 3001 is prime: " + test.isPrime(3001));do you see how my methods resized it?
here is the output:
[F F T T F T F T F F F T F T F F F]
There are 6 prime nummbers in the sieve from 1 to 15.
There are 15 prime numbers in the resized sieve from 1 to 25.
The first 25 prime numbers are:
[2 3 5 7 11 13 17 19 23 29 31 37 41 43 47]// this is only the first 15 elements
The 13th prime number is: 41
The number 3001 is prime: true
thanks for taking your time to look at this

What's the problem?
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1005323 wrote:
Hello guys,
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You may fail to get a job after without achieving Pl/sql developer OCA
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Write a Pl/SQL program using While loop , which will accept integer from 1 to 50 and generate the prime numbers as showen in the following output :
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HanyFreedom is one of the oracle's teachers that I have asked him yesterday about this Question .. I just know him via the internet ..
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Message was edited by:
user635582

Help me getting prime numbers

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