Java中的回文数字

Question

我写程序来解决几个关于数字的问题。我的程序应该：

>

欢迎用户；

如果一个数字不是自然的，打印一个错误消息；

打印自然数的属性；

在处理完请求后，继续从步骤3开始执行。

package numbers;

import java.util.Scanner;

public class Main {
public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);
    System.out.println("Welcome to Amazing Numbers!\n" +
            "\n" +
            "Supported requests:\n" +
            "- enter a natural number to know its properties;\n" +
            "- enter 0 to exit.\n" +
            "\n" +
            "Enter a request:");
    int number = scanner.nextInt();
    if (number >= 0) {
        System.out.println("Properties of " + number);
        System.out.println("\t even: " + (number % 2 == 0));
        System.out.println("\t odd: " + (number % 2 != 0));
        System.out.println("\t buzz: " + checkBuzzNumber(number));
        System.out.println("\t duck: " + checkDuckNumber(number));
        System.out.println("\t palindromic: " + checkPalindromicNumber(number));
    } else {
        System.out.println("The first parameter should be a natural number or zero.");
    }
}

public static boolean checkBuzzNumber(int number) {
    return number % 7 == 0 || String.valueOf(number).endsWith("7");
}

public static boolean checkDuckNumber(int number) {
    String num = String.valueOf(number);
    boolean flag = false;
    if (num.startsWith("0")) {
        return false;
    } else {
        for (int i = 1; i < num.length(); i++) {
            if (num.charAt(i) == '0') {
                flag = true;
                break;
            }
        }
        return flag;
    }
}

public static boolean checkPalindromicNumber(int number) {
    int rem, rev = 0, temp;
    temp = number;
    while (number != 0) {
        rem = number % 10;
        rev = rev * 10 + rem;
        number = number / 10;
    }
    if (temp == rev)
        return true;
    else
        return false;
}

Answer 1

您只需要一个循环就可以得到所需的输出，下面是代码和注释，以便正确理解。另外，我已经评论了你写的代码，但我从那里删除了。

import java.util.Scanner;

public class Main {
public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);
//    System.out.println("Welcome to Amazing Numbers!\n" +
//            "\n" +
//            "Supported requests:\n" +
//            "- enter a natural number to know its properties;\n" +
//            "- enter 0 to exit.\n" +
//            "\n" +
//            "Enter a request:");
//    int number = scanner.nextInt();
    
    //-------------------------------------------------------------
    while (true)// added an infinite while loop, in order to display and take input continuously
    {
        System.out.println("Welcome to Amazing Numbers!\n" +
                "\n" +
                "Supported requests:\n" +
                "- enter a natural number to know its properties;\n" +
                "- enter 0 to exit.\n" +
                "\n" +
                "Enter a request:");
        int number = scanner.nextInt();
        
        if (number == 0)//  checks for the number to be zero or not.
        {
            break;      // jump statement, breaks out of the loop.
        }
        
        if (number > 0) {// if entered number is greater than zero, 
            System.out.println("Properties of " + number);
            System.out.println("\t even: " + (number % 2 == 0));
            System.out.println("\t odd: " + (number % 2 != 0));
            System.out.println("\t buzz: " + checkBuzzNumber(number));
            System.out.println("\t duck: " + checkDuckNumber(number));
            System.out.println("\t palindromic: " + checkPalindromicNumber(number));
            System.out.println();// for a new line
        } 
        else // if number is less than zero,
        {
            System.out.println("The first parameter should be a natural number or zero.\n");
        }
        
    }
    
    scanner.close();//good practice to close the scanner.
    
    
    //____________________________________________________________
//    if (number >= 0) {
//        System.out.println("Properties of " + number);
//        System.out.println("\t even: " + (number % 2 == 0));
//        System.out.println("\t odd: " + (number % 2 != 0));
//        System.out.println("\t buzz: " + checkBuzzNumber(number));
//        System.out.println("\t duck: " + checkDuckNumber(number));
//        System.out.println("\t palindromic: " + checkPalindromicNumber(number));
//    } else {
//        System.out.println("The first parameter should be a natural number or zero.");
//    }
}

public static boolean checkBuzzNumber(int number) {
    return number % 7 == 0 || String.valueOf(number).endsWith("7");
}

public static boolean checkDuckNumber(int number) {
    String num = String.valueOf(number);
    boolean flag = false;
    if (num.startsWith("0")) {
        return false;
    } else {
        for (int i = 1; i < num.length(); i++) {
            if (num.charAt(i) == '0') {
                flag = true;
                break;
            }
        }
        return flag;
    }
}

public static boolean checkPalindromicNumber(int number) {
    int rem, rev = 0, temp;
    temp = number;
    while (number != 0) {
        rem = number % 10;
        rev = rev * 10 + rem;
        number = number / 10;
    }
    if (temp == rev)
        return true;
    else
        return false;
}

}