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Old February 13th, 2006, 05:48 PM
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Default Very, very introductory question...

Hi there -- I am trying to follow through the Wrox book "Beginning Java 2, Version 5," despite the fact that it is largely aimed at PCs and I am on a Mac...as well as the fact that I cannot install JDK 5 because I am on OSX 10.3.9, which only allows up to SDK 1.4!

I was attempting to compile a program which imports two math classes using this basic form: "import static java.lang.Math.sqrt" and also Math.ceil ....

I am compiling and editing them using XCode.

But for some reason these statements does not work. I know that I am typing them correctly, and in fact when I take away the "static" element of the import statement, it reduces the errors produced from 5 to 2, but there are still those two errors because allegedly java.lang.Math.sqrt and .ceil cannot be found!

When I import Math.*, that seems to work fine, but when I make a call to the sqrt or ceil classes, there is an error. Why would these functions not be in java.lang.Math.* ?? Surely sqrt and ceil are not new additions from 1.4 to 5??

Thanks for any help!
-matt
 
Old February 13th, 2006, 06:46 PM
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Default

okay...i modified it so that i didn't start the code with the offending statement, "import static java.lang.Math.sqrt" -- instead, i made a call to java.lang.Math.sqrt from WITHIN the code...somehow THIS works, even though attempting to import it at the top of the code gives me the error "<identifier> expected." why would this be???

also, in the original code, there is a line: "for(long n : primes)" which does not compile when i try it. the error message points to that line and says "; expected." whaaa? i replaced it with for(int i = 0; i < primes.length; i++), which does the same thing, but i am perplexed as to why the original line wouldn't have worked.

please help!

here is the code as i have MODIFIED it:

public class MorePrime {
    public static void main(String[] args) {
        long[] primes = new long[20];
        primes[0] = 2L;
        primes[1] = 3L;
        int count = 2;

        long number = 5L;

        outer:
        for( ; count < primes.length; number += 2L) {
            long limit = (long)java.lang.Math.ceil(java.lang.Math.sqrt((dou ble)number));

            for(int i = 1; i < count && primes[i] <= limit; i++) {
                if(number%primes[i] == 0L) {
                    continue outer;
                }
            }
            primes[count++] = number;
        }

        for(int i = 0; i < primes.length; i++) {
            System.out.println(primes[i]);
        }
    }
}






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