3.12（回文数字）编写一个程序，提示用户输入一个三位的整数，然后确定它是否是回文数。如果一个数字从左到右以及从右到左都是一样的，这个数字称为回文数。负数的处理和正数一样。 下面是程序的一个运行示例： Enter a three-digit integer:121 121 is a palindrome Enter a three-digit integer:123 123 is not a palindrome
3.12(Palindrome integer) Write a program that prompts the user to enter a three-digit integer and determines whether it is a palindrome integer. An integer is palindrome if it reads the same from right to left and from left to right. A negative integer is treated the same as a positive integer. Here are sample runs of this program: Enter a three-digit integer:121 121 is a palindrome Enter a three-digit integer:123 123 is not a palindrome
参考代码：
方法一：package chapter03; import java.util.Scanner; public class Code_12 { public static void main(String[] args){ Scanner input = new Scanner(System.in); System.out.print("Enter a three-digits integer: "); String str1 = input.nextLine(); String str2 = ""; for (int i = str1.length() - 1;i >= 0;i--){ str2 += str1.charAt(i); } if (str1.equals(str2)) System.out.println(str1 + " is a palindrome"); else System.out.println(str1 + " is not a palindrome"); } } 方法二：package chapter03; import java.util.Scanner; public class Code_12another { public static void main(String[] args) { int number; System.out.print("Enter a three-digit integer number: "); Scanner input = new Scanner(System.in); number = input.nextInt(); if(number / 100 == number % 10) System.out.println(number + " is a palindrome"); else System.out.println(number + " is not a palindrome"); input.close(); } }结果显示：
Enter a three-digit integer number: 121 121 is a palindrome Process finished with exit code 0