如何让Java闰年程序循环运行直至输入0退出？

问题描述 #

我正在完成编程入门课程的期末作业，无法实现让Java闰年程序循环运行直至用户输入0退出的功能。老师要求必须使用指定代码格式，不允许简化代码。整个16周课程中仅学习了约4周Java，对Java的使用和理解较为生疏。

目前程序可接收年份输入、判断是否为闰年、输出对应结果后直接退出。checkValidYear方法会输出提示语“如果想退出请输入0。”，但无法接收后续输入。需要指导修改程序，使其循环运行直至用户输入0才停止。

当前代码 #

主文件代码（FinalProject.java） #

/**
 * Main class of the Java program.
 */
import java.util.Scanner;

public class FinalProject {

    public static void main(String[] args) {
        
        
        int usersYear;
        
        //set up the scanner
        Scanner inputReader = new Scanner(System.in);
        
        //Create leap year instance
        LeapYear inputYear = new LeapYear();
      
    do { 
        System.out.println("Enter a year which I will test if it is a leap year. Input 0  to stop");
        
        
        int i = inputReader.nextInt();
        inputYear.setYear(i);
       }
        
         while(inputYear.checkValidYear().equals("invalid"));
        inputReader.close();
        System.out.println(inputYear.getOutput());

       // create a loop to which sees if the user wants to stop
        //   in the loop:
        //     use the setYear() method to set the year inside the object
        //     use the CheckforLeapYear() method to do all the testing. DO NOT SEND YEAR because it was already set using setYear()
        //     use the getOutput() to get the message you print - is it a leap year or not.
        //     get the next year from the user
            
        
        
    } //end main method
} //end Main class 

LeapYear类代码（LeapYear.java） #

/**
 LeapYear class determines if a year is a leap year
**/
class LeapYear {
    /**Declarations**/
    /*
    * 1. Create a private year variable that is an integer 
    * 2. Create a getter and setter method for the field variable
    * 3. Create a default constructor.Do not set any variables
    **/
  private int year;
  
  public LeapYear(){
      
  }
  
  // Getter
     public int getYear() {
        return year;
  }

  // Setter
     public void setYear(int newYear) {
        year = newYear;
  }
  
  
    /*
    * This method should call all the checkIfYearDivisibleby4(), checkIfYearNotDivisibleby100(), and checkIfYearDivisibleby400()
    * @return int year
    **/
    public boolean checkForLeapYear(){
        boolean result = false;
        //add code here
      result= checkIfYearDivisibleby4()||
        checkIfYearNotDivisibleby100()||
        checkIfYearDivisibleby400();
      
        return result;
    }
  
    /*
    * This method should return true if year is divisible by 4
    * @return int year
    **/
    private boolean checkIfYearDivisibleby4(){
        boolean result = false;
            //add code here
            result = year%4==0;
            return result;
    }   
    
    /*
    * This method should return true if year is NOT divisible by 100
    * @return int year
    **/
    private boolean checkIfYearNotDivisibleby100(){
        boolean result = false;
        //add code here
        result = year%100==0;
        return result;
            
    }
  
    /*
    * This method should return true if year is divisible by 400
    * @return int year
    **/     
    private boolean checkIfYearDivisibleby400(){
        boolean result = false;
        //add code here
        result = year%400==0;
        return result;

    }
  
    /*
    * This method calls the checkForLeapYear()
    * if the checkForLeapYear() returns true return a string that states it is a leap year
    * otherwise, return a string that states it is not a leap year
    * @return int year
    **/
      
      public String getOutput(){
      String output= "";
      if (checkForLeapYear())
      {
          output = "This is a leap year";
      }
      else
      {
          output = "This is not a leap year";
      }
      return output;
    }
    
    public String checkValidYear(){
        System.out.println("Enter 0 if you'd like to exit.");
        String result = "valid";
        if(year==0)
        result = "invalid";
        return result;
    
        
    }
    

}

当前程序输出 #

Enter a year which I will test if it is a leap year. Input 0  to stop
2023
Enter 0 if you'd like to exit.
This is not a leap year

修复步骤及修改后代码 #

1. 修正LeapYear类中的逻辑错误 #

你的闰年判断逻辑存在两处核心错误：

• checkIfYearNotDivisibleby100方法：方法名要求返回“年份不能被100整除”的结果，但当前代码返回year%100==0（即能被100整除），逻辑完全相反，需改为year%100 != 0。
• checkForLeapYear方法：闰年的正确规则是能被4整除，且（不能被100整除 或 能被400整除），当前用||串联所有条件的逻辑错误，需调整为checkIfYearDivisibleby4() && (checkIfYearNotDivisibleby100() || checkIfYearDivisibleby400())。

修改后的LeapYear类关键方法：

// 修正checkIfYearNotDivisibleby100方法
private boolean checkIfYearNotDivisibleby100(){
    boolean result = false;
    result = year%100 != 0; // 改为不等于0
    return result;
}

// 修正checkForLeapYear方法
public boolean checkForLeapYear(){
    boolean result = false;
    result = checkIfYearDivisibleby4() && (checkIfYearNotDivisibleby100() || checkIfYearDivisibleby400());
    return result;
}

// 提示语改为中文（可选）
public String checkValidYear(){
    System.out.println("如果想退出请输入0。");
    String result = "valid";
    if(year==0)
        result = "invalid";
    return result;
}

2. 修改主程序的循环结构 #

当前主程序的do-while循环条件颠倒，且输出仅在循环外执行一次。需要将输入、判断、输出全部放入循环内，直到用户输入0才退出：

修改后的FinalProject.java主方法：

public static void main(String[] args) {
    
    int usersYear;
    
    //set up the scanner
    Scanner inputReader = new Scanner(System.in);
    
    //Create leap year instance
    LeapYear inputYear = new LeapYear();
  
    do { 
        System.out.println("请输入一个年份，我会判断它是否为闰年。输入0退出");
        
        int i = inputReader.nextInt();
        inputYear.setYear(i);
        
        // 如果输入的是0，直接退出循环
        if(i == 0){
            System.out.println("程序已退出");
            break;
        }
        
        // 输出闰年判断结果
        System.out.println(inputYear.getOutput());
        
    } while(true); // 无限循环，直到输入0时break
    
    inputReader.close();
}

3. 调整输出提示语为中文（可选） #

若需要全中文输出，可修改getOutput方法：

public String getOutput(){
    String output= "";
    if (checkForLeapYear())
    {
        output = "这是闰年";
    }
    else
    {
        output = "这不是闰年";
    }
    return output;
}

修复后程序运行示例 #

请输入一个年份，我会判断它是否为闰年。输入0退出
2020
这是闰年
请输入一个年份，我会判断它是否为闰年。输入0退出
2023
这不是闰年
请输入一个年份，我会判断它是否为闰年。输入0退出
0
程序已退出

内容的提问来源于stack exchange，提问作者imadethisaccountformyfinal