方法不會拿起用戶輸入

Question

我寫的程序是確定今年是否是閏年。這是一項任務，所以我需要使用我在程序中編寫的四種方法。該程序編譯並運行，它要求在適當的地方進行用戶輸入，但不會將輸入輸入到程序中。也就是說，無論輸入什麼內容，今年都是閏年。我非常困惑，因爲這個程序看起來與我們給出的例子相匹配。

import java.util.Scanner; 

public class LeapYear { 
    public static void main(String[] args) { 
     boolean repeat; 
     String computeanother, yes="yes"; 
     Scanner kb=new Scanner(System.in); 
     int year = -1; 
     boolean leap; 

     do 
     { 
      displayInstructions(); 
      getYear(year); 
      leap = isLeap(year); 
      displayResults(year, leap); 
      System.out.println("Would you like to compute another year?"); 
      computeanother = kb.nextLine(); 

      if(computeanother.equals(yes)) 
       repeat=true; 
      else 
       repeat=false; 
     } while(repeat=true); 
    } 

    public static void displayInstructions() 
    { 
     System.out.println("This program is designed to predict whether or not a year is a leap year."); 
     System.out.println("When prompted please enter a positive number for the year."); 
     System.out.println("Once the program has run completely, it will state the year and whether it is a leap year."); 
    } 

    public static void getYear(int year) 
    { 
     Scanner kb = new Scanner(System.in); 
     do { 
      System.out.println("Please enter the year."); 
      year=kb.nextInt(); 
     } while (year < 0); 
    } 

    public static boolean isLeap(int year) 
    { 
     boolean leap; 
     if ((year%4==0 && year%100 != 0) || year%400==0){ 
      leap = true; 
      return true; 
     } else { 
      leap = false; 
      return false; 
     } 
    } 

    public static void displayResults(int year, boolean leap) 
    { 
     if (leap = true) { 
      System.out.println("The year " +year); 
      System.out.println("is a leap year."); 
     } else { 
      System.out.println("The year " +year); 
      System.out.println("is not a leap year."); 
     } 
    } 

} 

感謝大家的幫忙！編輯後的代碼如下所示：

import java.util.Scanner; 

public class LeapYear{ 
public static void main(String[] args){ 
boolean repeat; 
String computeanother, yes="yes"; 
Scanner kb=new Scanner(System.in); 
int year = -1; 
boolean leap; 
do 
{ 
displayInstructions(); 
getYear(year); 
leap = isLeap(year); 
displayResults(year, leap); 
System.out.println("Would you like to compute another year?"); 
computeanother = kb.nextLine(); 
repeat = computeanother.equals(yes); 
}while(repeat); 
} 
public static void displayInstructions() 
{ 
System.out.println("This program is designed to predict whether or not a year is a leap year."); 
    System.out.println("When prompted please enter a positive number for the year."); 
System.out.println("Once the program has run completely, it will state the year and whether it is a leap year."); 
} 

public static int getYear(int year) 
{ 
    Scanner kb = new Scanner(System.in); 
    do{ 
     System.out.println("Please enter the year."); 
     year=kb.nextInt(); 
    }while (year < 0); 
    return year; 
} 

public static boolean isLeap(int year) 
{ 
boolean leap; 
year = getYear(year); 
if ((year%4==0 && year%100 != 0) || year%400==0){ 
    leap = true; 
    return true;} 
else{ 
    leap = false; 
    return false;} 
} 

public static int displayResults(int year, boolean leap) 
{ 
year = getYear(year); 
if (leap == true){ 
    System.out.println("The year " +year); 
    System.out.println("is a leap year.");} 
else{ 
    System.out.println("The year " +year); 
    System.out.println("is not a leap year.");} 
return year; 
} 

} 

Answer 1

更改此：

while(repeat=true); 

到

while(repeat==true); 

或

while(repeat); 

這裏while(repeat=true);你正在分配一個值，而不是比較。 while(repeat==true);或while(repeat);這將比較值。測試像這樣while(repeat);而不是明顯的while(repeat==true);總是更好。我希望它有幫助。

而你不year獲得價值爲-1，因爲，你是從這個方法返回getYear(year);而忽視價值。將其更改爲：

year = getYear(year);

這應該工作。

Answer 2

while(repeat=true); 

在while循環應該是：

while(repeat == true); 

或

while(repeat); 

從這個

除了被大家所指出的，可以注意到你犯了這種錯誤兩次：

if (leap = true) { 

應該是：

if (leap == true) { 

或

if (leap) { 

Answer 3

您也可以縮短你的代碼：

do{ 
     displayInstructions(); 
     getYear(year); 
     leap = isLeap(year); 
     displayResults(year, leap); 
     System.out.println("Would you like to compute another year?"); 
     computeanother = kb.nextLine(); 
     repeat = computeanother.equals(yes) //this line makes code shorter 
    } while(repeat); 

事實上，總是避免這樣的著名模式的冗餘代碼：

if(expression) return true; else return false; 

變成：return expression;