**6.26 (Palindromic prime) A palindromic prime is a prime number and also palindromic.
For example, 131 is a prime and also a palindromic prime, as are 313 and
757. Write a program that displays the first 100 palindromic prime numbers. Display
10 numbers per line, separated by exactly one space, as follows:
2 3 5 7 11 101 131 151 181 191
313 353 373 383 727 757 787 797 919 929
2 3 5 7 11 101 131 151 181 191
313 353 373 383 727 757 787 797 919 929
public class ProgrammingExercise6_26 { public static void main(String[] args) { final int NUMBER_OF_PALINPRIME = 100; int numberPrinted = 0, testedNumber = 2; while (numberPrinted < NUMBER_OF_PALINPRIME) { if (isPrime(testedNumber) && isPalindrome(testedNumber)) { numberPrinted++; System.out.print(testedNumber + " "); if (numberPrinted % 10 == 0) { System.out.println(); } } testedNumber++; } } /** Check whether number is prime */ public static boolean isPrime(int number) { for (int divisor = 2; divisor <= number / 2; divisor++) { if (number % divisor == 0) { // If true, number is not prime return false; // number is not a prime } } return true; // number is prime } public static int reverse(int number) { int reverse = 0; int digit; do { digit = number % 10; reverse = reverse * 10 + digit; number /= 10; } while (number != 0); return reverse; } public static boolean isPalindrome(int number) { return (number == reverse(number)); } }
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