Better way to check a number for Prime. Update PrimeCheck.java

[ZingadePrathamesh]

The function does this by

1. Skip even numbers (except 2) since they are not prime.
2. Skip multiples of 3 after checking 3.
3. Start checking for factors from 5 and use the 6k ± 1 optimization. This is based on the fact that any prime number greater than 3 can be expressed as 6k ± 1.

This helps to make it much more efficient for large numbers.

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 51.20%. Comparing base (fa22317) to head (07368ad).

Files with missing lines	Patch %	Lines
.../main/java/com/thealgorithms/maths/PrimeCheck.java	0.00%	10 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5259      +/-   ##
============================================
- Coverage     51.25%   51.20%   -0.05%     
+ Complexity     3192     3191       -1     
============================================
  Files           524      524              
  Lines         15194    15204      +10     
  Branches       2893     2898       +5     
============================================
- Hits           7787     7785       -2     
- Misses         7084     7095      +11     
- Partials        323      324       +1     

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[alxkm]

Please, fix formatting issues, and update branch, and we can start review.

[ZingadePrathamesh]

I don't know how to do format. This is my first pull request. I will try again soon

…

On Thu, 8 Aug 2024 at 13:23, Alex Klymenko ***@***.***> wrote: Please, fix formatting issues, and update branch, and we can start review. — Reply to this email directly, view it on GitHub <#5259 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AYJIQWW4MUIGE5IBHCW53SLZQMPX7AVCNFSM6AAAAABJ7EVAS2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDENZVGE4DCMZTGY> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[vil02]

I don't know how to do format. This is my first pull request. I will try again soon

Just run clang-format. If you are having problems with that, please inspect the log:
https://github.com/TheAlgorithms/Java/actions/runs/9691003340/job/26741793012?pr=5259
It seams that you just need to remove some double spaces in few places - it can definitely be done manually.

[ZingadePrathamesh]

I don't know how to do format. This is my first pull request. I will try again soon

Just run clang-format. If you are having problems with that, please inspect the log: https://github.com/TheAlgorithms/Java/actions/runs/9691003340/job/26741793012?pr=5259 It seams that you just need to remove some double spaces in few places - it can definitely be done manually.

I guess the code is good to go now.

[alxkm]

What do you think about removing these comments and moving them to the Javadoc? Because the code of this method is quite simple, but all these descriptions are harder to read: and after deleting it should be:

/**
 * Determines if a given number is prime using an optimized approach.
 * <p>
 * This method checks for primality with the following steps:
 * <ul>
 *   <li>Numbers less than or equal to 1 are not prime.</li>
 *   <li>Numbers 2 and 3 are prime.</li>
 *   <li>Eliminates even numbers and multiples of 3 early for efficiency.</li>
 *   <li>Uses the 6k ± 1 optimization for checking factors, which skips even numbers
 *       and multiples of 3 to cover all other possible factors.</li>
 *   <li>If no factors are found up to the square root of the number, the number is prime.</li>
 * </ul>
 * 
 * @param number the number to check
 * @return true if the number is prime, false otherwise
 */
public static boolean isPrimeNumberOptimised(long number) {
    if (number <= 1) return false;
    if (number <= 3) return true;
    if (number % 2 == 0 || number % 3 == 0) return false;
    for (long i = 5; i * i <= number; i += 6) {
        if (number % i == 0 || number % (i + 2) == 0) {
            return false;
        }
    }
    return true;
}