回文数

回文数(或回文数)是指一个像14641这样“对称”的数，即：将这个数的数字按相反的顺序重新排列后，所得到的数和原来的数一样。这里，“回文”是指像“妈妈爱我，我爱妈妈”这样的，正读反读都相同的单词或句子。

回文数在休闲数学领域备受关注。一个典型的问题就是，寻找那些具有某种特性，并且符合回文特征的数。例如：

回文素数：2, 3, 5, 7, 11, 101, 131, 151,…
回文完全平方数：0, 1, 4, 9, 121, 484, 676, 10201, 12321,…

public class PalindromeExample1 {
	public static void main(String args[]) {
		int r, sum = 0, temp;
		int n = 454;// It is the number variable to be checked for palindrome

		temp = n;
		while (n > 0) {
			r = n % 10; // getting remainder
			sum = (sum * 10) + r;
			n = n / 10;
		}
		if (temp == sum)
			System.out.println("palindrome number ");
		else
			System.out.println("not palindrome");
	}
}

点击查看结果

“`
palindrome number
“`

import java.util.Scanner;
public class PalindromeExample2 {
	public static void main(String args[]) {
		String original, reverse = ""; // Objects of String class
		Scanner in = new Scanner(System.in);
		System.out.println("Enter a string/number to check if it is a palindrome");
		original = in.nextLine();
		int length = original.length();
		for (int i = length - 1; i >= 0; i--)
			reverse = reverse + original.charAt(i);
		if (original.equals(reverse))
			System.out.println("Entered string/number is a palindrome.");
		else
			System.out.println("Entered string/number isn't a palindrome.");
		in.close();
	}
}