Exercise05_20.java

package ch_05;

import java.util.*;

/**
 * 5.20 (Display prime numbers between 2 and 1,000) Modify Listing 5.15 to display all
 * the prime numbers between 2 and 1,000, inclusive. Display eight prime numbers
 * per line. Numbers are separated by exactly one space.
 *
 * Example output:
 * Prime nums between 2 and 1000 are:
 * 2 3 5 7 11 13 17 19
 * 23 29 31 37 41 43 47 53
 * 59 61 67 71 73 79 83 89
 * 97 101 103 107 109 113 127 131
 * 137 139 149 151 157 163 167 173
 * 179 181 191 193 197 199 211 223
 * 227 229 233 239 241 251 257 263
 * 269 271 277 281 283 293 307 311
 * 313 317 331 337 347 349 353 359
 * 367 373 379 383 389 397 401 409
 * 419 421 431 433 439 443 449 457
 * 461 463 467 479 487 491 499 503
 * 509 521 523 541 547 557 563 569
 * 571 577 587 593 599 601 607 613
 * 617 619 631 641 643 647 653 659
 * 661 673 677 683 691 701 709 719
 * 727 733 739 743 751 757 761 769
 * 773 787 797 809 811 821 823 827
 * 829 839 853 857 859 863 877 881
 * 883 887 907 911 919 929 937 941
 * 947 953 967 971 977 983 991 997
 *
 * @author Harry Dulaney
 */
public class Exercise05_20 {
    public static void main(String[] args) {

        int nextLineCount = 8;
        for (int i = 2; i <= 1000; i++) {

            if (isPrime(i)) {
                System.out.print(i + " ");
                --nextLineCount;
                if (nextLineCount == 0) {
                    System.out.println();
                    nextLineCount = 8;
                }
            }
        }
    }

    static boolean isPrime(int n) {
        boolean notPrime = false;
        int d = 2;
        while (d <= n / 2) {
            if (n % d == 0) {
                notPrime = true;
                break;
            }
            ++d;
        }
        return !notPrime;

    }
}