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  1. Optimizing the Sieve of Eratosthenes

    The Sieve of Eratosthenes is one of the fastest methods for generating a list of prime numbers less than a given number n. A general description of the algorithm is given below:

    1. Initialize a list representing the numbers [2,n). This denotes whether a given number is prime or composite.
    2. Start from the beginning of the list. If the number is denoted as prime, save it. Otherwise, move on.
    3. For every multiple of the current prime, mark it as a composite number. ...

    Updated September 29th, 2012 at 07:26 PM by helloworld922

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  2. Preview: 2D Grid Accelerator Structure

    This is a short preview of 2D grid accelerator structure. It's primary use is for speeding up collision detection.

    The general concept is this:

    The full 2D space is partitioned into individual grid (the black lines). Each shape added to the grid has some minimal aligned bounding box (pictured as green outlines). Every grid square which overlaps this bounding box has the shape's reference added to it's list of shapes (red background). Now to check for collisions, you ...

    Updated April 8th, 2012 at 11:59 PM by helloworld922

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  3. Thread Volatility

    Summary
    This is put at the top for those who don't want to read the entire thing.
    • Threads get more volatile as more are added, up to a point
    • Thread volatility jumps drammatically on my computer between 4 and 8 threads.
    • Calling non-volatile variables is very inaccurate


    Overview
    I recently posted a forum thread that more Java Threads will increase volatility. While I had seen the side-effect volatility and it seemed intuitive enough, I decided that n order ...

    Updated March 13th, 2012 at 03:26 PM by Tjstretch

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  4. Enhanced For Statement - JavaDevelopmentForums.com

    When working with arrays, there's an easier way to loop through the indices than manually doing so. We can use the enhanced for statement for this.

    class Class1{
       public static void main(String args[]){
    	   int aryOne[] = {3,4,5,6,7};
    	   int total = 0;
    	   for (int x: aryOne){
    		   total += x;
    	   }
    	   System.out.println(total);
       }
    }

    First of all, we create our array (aryOne) and use ...
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  5. Array Elements As Counters - JavaDevelopmentForums.com

    We're going to build a program to re-enact a dice being rolled one thousand times. We're going to output how many times each face of the dice is rolled.

    import java.util.Random;
     
    class RollDice{
       public static void main(String args[]){
    	   Random rand = new Random();
    	   int freq[] = new int[7];
     
    	   for(int roll = 1; roll <= 1000; roll++){
    		   ++freq[1 + rand.nextInt(6)];
    	   }
    	   System.out.println("Face\tFrequency");
    ...
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