PrimeGetter.java

package others;
import lessones01.LinkedList;
public class PrimeGetter{
	private static LinkedList<Integer> primes = new LinkedList<Integer>();
	public static int get(int arg_num){
		for(int i = primes.size()-1;i<arg_num;i++){add();}
		return primes.get(arg_num);
	}
	private static void add(){
		int size = primes.size();
		if(size == 0){
			primes.add(2);
		}else if(size == 1){
			primes.add(3);
		}else{
			for(int x = primes.get(size-1)+2;;x+=2){
				boolean isPrime = true;
				int floatPrime;
				int z = (int)Math.sqrt(x);
				for(int i=1;i<size;i++){
					if(x%(floatPrime = primes.get(i)) == 0){
						isPrime = false;
						break;
					}
					if(z<floatPrime){break;}
				}
				if(isPrime){
					primes.add(x);
					return;
				}
			}
		}
	}
	public static boolean isPrime(int arg_num){
		int i = 0;
		for(;arg_num>get(i);i++){}
		return arg_num == primes.get(i);
	}
}