Our Prime Numbers code in Java.
Prime Numbers Class File:
package arithmetic;
import java.util.ArrayList; // We are using an array list.
import java.util.List;
public class PrimeNumbers {
private final List<Integer> list_of_primes; // We will house our gathered prime numbers here.
private final int start; // Where to start.
private final int stop; // Where to stop.
private int progress; // progress report
private int index; // index into array list_of_primes
private double square_root; // Our loop range for speed enhancement
private boolean do_next_iteration;
public PrimeNumbers(int first, int last) {
start = first;
stop = last;
// STEP 1:
progress = 9;
list_of_primes = new ArrayList<>();
list_of_primes.add(2);
list_of_primes.add(3);
list_of_primes.add(5);
list_of_primes.add(7);
square_root = 0;
}
/**
* Garners the prime numbers between the requested range.
*
* @return String value
*/
public String getPrimes() {
// STEP 2:
for (; progress < stop; progress += 2) {
do_next_iteration = false; // a flag
// STEPS 3, 4:
// Check through already accumulated prime numbers
// to see if any is a factor of "progress".
square_root = (int) Math.ceil(Math.sqrt(progress));
index = 0;
for (; list_of_primes.get(index) <= square_root; index++) {
if ((progress % list_of_primes.get(index)) == 0) {
do_next_iteration = true;
break;
}
}
if (do_next_iteration) {
continue;
}
// if all checks are scaled,then "progress" is our guy.
list_of_primes.add(progress);
}
// Display result.
return ("The set of prime numbers between " + start + " and " + stop
+ " are: \n" + list_of_primes);
}
}Main Class:
package arithmetic;
public class Arithmetic {
public static void main(String[] args) {
System.out.println("Welcome to our demonstration sequels");
System.out.println("Hope you enjoy (and follow) the lessons.");
System.out.println("");
/*
* List Prime Numbers.
*/
PrimeNumbers my_list = new PrimeNumbers(5, 500);
System.out.println(my_list.getPrimes());
}
}Try it out!
Elegance (0.0)
