混淆，为什么不能调用”void passenger”，而且没有任何错误。

huangapple
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英文:

Confusing, why not able to call out void passenger and there is no any error

问题

  1. import java.util.Scanner;
  3. public class Elevator {
  4.     private int currentFloor;
  5.     private static final int MAXFLOOR = 15;
  6.     int newFloor;
  7.     int newP;
  8.     int currentP = 1;
  9.     int maxP = 20;
  11.     public Elevator() {
  12.         currentFloor = 1;
  13.     }
  15.     public void passenger() {
  16.         Scanner scanner1 = new Scanner(System.in);
  17.         System.out.println("Enter total passenger: ");
  18.         newP = scanner1.nextInt();
  19.         if (newP > maxP || newP == currentP) {
  20.             System.out.println("Invalid passenger number");
  21.             passenger();
  22.         } else {
  23.             if (newP < currentP) {
  24.                 minPassenger();
  25.             } else if (newP > currentP) {
  26.                 maxPassenger();
  27.             }
  28.         }
  29.         passenger();
  30.     }
  32.     public void maxPassenger() {
  33.         System.out.println("Maximum passenger");
  34.     }
  36.     public void minPassenger() {
  37.         System.out.println("0 passenger, not acceptable");
  38.     }
  40.     public void display(Object a) {
  41.         System.out.println(a);
  42.     }
  44.     public void request(Object a) {
  45.         System.out.println(a);
  46.     }
  48.     public void delay(int ms) {
  49.         try {
  50.             Thread.sleep(ms);
  51.         } catch (Exception e) {
  52.         }
  53.     }
  55.     public void moveUp() {
  56.         System.out.println("Starting at floor " + currentFloor);
  57.         while (currentFloor++ < newFloor) {
  58.             System.out.println("Going up -  now at floor " + currentFloor);
  59.             delay(600);
  60.         }
  61.         currentFloor--;
  62.         System.out.println("Stopping at floor " + newFloor);
  63.     }
  65.     public void moveDown() {
  66.         System.out.println("Starting at floor " + currentFloor);
  67.         while (currentFloor-- > newFloor) {
  68.             System.out.println("Going down -  now at floor " + currentFloor);
  69.             delay(600);
  70.         }
  71.         currentFloor++;
  72.         System.out.println("Stopping at floor " + newFloor);
  73.     }
  75.     public void request() {
  76.         Scanner scanner = new Scanner(System.in);
  77.         System.out.println("Enter new floor: ");
  78.         newFloor = scanner.nextInt();
  79.         if (newFloor > MAXFLOOR || newFloor == currentFloor) {
  80.             System.out.println("INCORRECT FLOOR NUMBER, NO ACTION TAKEN");
  81.             request();
  82.         } else {
  83.             if (newFloor < currentFloor) {
  84.                 moveDown();
  85.             } else if (newFloor > currentFloor) {
  86.                 moveUp();
  87.             }
  88.         }
  89.         request();
  90.     }
  92.     public static void main(String[] args) {
  93.         Elevator e = new Elevator();
  94.         e.request();
  95.         e.passenger();
  96.     }
  97. }
英文:

I am new learner to Java. Need some advise from expert. I want to make the program to ask how many passenger when every selected floor reached. I notice if I removed the call request the loop will just work for one time. But I need it to keep repeat and repeat. Anyways to make it happen without remove any current other methods? Thanks.

  1. import java.util.Scanner;
  3. public class Elevator {
  4.     private int currentFloor;
  5.     private static final int MAXFLOOR = 15;
  6.     int newFloor;
  7.     int newP;
  8.     int currentP = 1;
  9.     int maxP = 20;
  11.     public Elevator() {
  12.         currentFloor = 1;
  13.     }
  15.     public void passenger() {
  16.         Scanner scanner1 = new Scanner(System.in);
  17.         System.out.println(&quot;Enter total passenger: &quot;);
  18.         newP = scanner1.nextInt();
  19.         if (newP &gt; maxP || newP == currentP) {
  20.             System.out.println(&quot;Invalid passenger number&quot;);
  21.             passenger();
  22.         }
  23.         else {
  24.             if (newP &lt; currentP) {
  25.                 minPassenger();
  26.             }
  27.             else if (newP &gt; currentP) {
  28.                 maxPassenger();
  30.             }
  31.         }
  32.         passenger();
  33.     }
  35.     public void maxPassenger() {
  36.         System.out.println(&quot;Maximum passenger&quot;);
  37.     }
  39.     public void minPassenger() {
  40.         System.out.println(&quot;0 passenger, not acceptable&quot;);
  41.     }
  43.     public void display(Object a) {
  44.         System.out.println(a);
  45.     }
  47.     public void request(Object a) {
  48.         System.out.println(a);
  49.     }
  51.     public void delay(int ms) {
  52.         try {
  53.             Thread.sleep(ms);
  54.         }
  55.         catch (Exception e) {
  56.         }
  57.     }
  59.     public void moveUp() {
  60.         System.out.println(&quot;Starting at floor &quot; + currentFloor);
  61.         while (currentFloor++ &lt; newFloor) {
  62.             System.out.println(&quot;Going up -  now at floor &quot; + currentFloor);
  63.             delay(600);
  64.         }
  65.         currentFloor--;
  66.         System.out.println(&quot;Stopping at floor &quot; + newFloor);
  67.     }
  69.     public void moveDown() {
  70.         System.out.println(&quot;Starting at floor &quot; + currentFloor);
  71.         while (currentFloor-- &gt; newFloor) {
  72.             System.out.println(&quot;Going down -  now at floor &quot; + currentFloor);
  73.             delay(600);
  74.         }
  75.         currentFloor++;
  76.         System.out.println(&quot;Stopping at floor &quot; + newFloor);
  77.     }
  79.     public void request() {
  80.         Scanner scanner = new Scanner(System.in);
  81.         System.out.println(&quot;Enter new floor: &quot;);
  82.         newFloor = scanner.nextInt();
  83.         if (newFloor &gt; MAXFLOOR || newFloor == currentFloor) {
  84.             System.out.println(&quot;INCORRECT FLOOR NUMBER, NO ACTION TAKEN&quot;);
  85.             request();
  86.         }
  87.         else {
  89.             if (newFloor &lt; currentFloor) {
  90.                 moveDown();
  91.             }
  92.             else if (newFloor &gt; currentFloor) {
  93.                 moveUp();
  95.             }
  96.         }
  97.         request();
  98.     }
  100.     public static void main(String[] args) {
  101.         Elevator e = new Elevator();
  102.         e.request();
  103.         e.passenger();
  104.     }
  105. }

答案1

得分: 0

这是您的 main() 方法。

  1. public static void main(String[] args) {
  2.     Elevator e = new Elevator();
  3.     while (e.currentFloor >= 0) {
  4.         e.request();
  5.         if (e.currentFloor >= 0) {
  6.             e.passenger();
  7.         }
  8.     }
  9. }
英文:

Here is your main() method.

  1. public static void main(String[] args) {
  2.     Elevator e = new Elevator();
  3.     e.request();
  4.     e.passenger();
  5. }

Method request() never ends, because the last line in that method is a call to itself. Hence the line e.passenger() is never executed.

You should put a while loop in method main() and decide on a way to terminate the loop, for example entering a floor which is negative. And remove the last line in method request() &ndash; likewise with method passenger(), remove the last line where you call the method again.

I believe the following code does what you want. Note that you only need to create a Scanner object once.

  1. import java.util.Scanner;
  3. public class Elevator {
  4.     private Scanner scanner;
  5.     private int currentFloor;
  6.     private static final int MAXFLOOR = 15;
  7.     int newFloor;
  8.     int newP;
  9.     int currentP = 1;
  10.     int maxP = 20;
  12.     public Elevator() {
  13.         currentFloor = 1;
  14.         scanner = new Scanner(System.in);
  15.     }
  17.     public void passenger() {
  18.         System.out.print(&quot;Enter total passenger: &quot;);
  19.         newP = scanner.nextInt();
  20.         if (newP &gt; maxP || newP == currentP) {
  21.             System.out.println(&quot;Invalid passenger number&quot;);
  22.             passenger();
  23.         }
  24.         else {
  25.             if (newP &lt; currentP) {
  26.                 minPassenger();
  27.                 passenger();
  28.             }
  29.             else if (newP &gt; currentP) {
  30.                 maxPassenger();
  31.             }
  32.         }
  33.     }
  35.     public void maxPassenger() {
  36.         System.out.println(&quot;Maximum passenger&quot;);
  37.     }
  39.     public void minPassenger() {
  40.         System.out.println(&quot;0 passenger, not acceptable&quot;);
  41.     }
  43.     public void display(Object a) {
  44.         System.out.println(a);
  45.     }
  47.     public void request(Object a) {
  48.         System.out.println(a);
  49.     }
  51.     public void delay(int ms) {
  52.         try {
  53.             Thread.sleep(ms);
  54.         }
  55.         catch (Exception e) {
  56.         }
  57.     }
  59.     public void moveUp() {
  60.         System.out.println(&quot;Starting at floor &quot; + currentFloor);
  61.         while (currentFloor++ &lt; newFloor) {
  62.             System.out.println(&quot;Going up -  now at floor &quot; + currentFloor);
  63.             delay(600);
  64.         }
  65.         currentFloor--;
  66.         System.out.println(&quot;Stopping at floor &quot; + newFloor);
  67.     }
  69.     public void moveDown() {
  70.         System.out.println(&quot;Starting at floor &quot; + currentFloor);
  71.         while (currentFloor-- &gt; newFloor) {
  72.             System.out.println(&quot;Going down -  now at floor &quot; + currentFloor);
  73.             delay(600);
  74.         }
  75.         currentFloor++;
  76.         System.out.println(&quot;Stopping at floor &quot; + newFloor);
  77.     }
  79.     public void request() {
  80.         System.out.print(&quot;Enter new floor: &quot;);
  81.         newFloor = scanner.nextInt();
  82.         if (newFloor &lt; 0) {
  83.             currentFloor = newFloor;
  84.             return;
  85.         }
  86.         if (newFloor &gt; MAXFLOOR || newFloor == currentFloor) {
  87.             System.out.println(&quot;INCORRECT FLOOR NUMBER, NO ACTION TAKEN&quot;);
  88.             request();
  89.         }
  90.         else {
  91.             if (newFloor &lt; currentFloor) {
  92.                 moveDown();
  93.             }
  94.             else if (newFloor &gt; currentFloor) {
  95.                 moveUp();
  96.             }
  97.         }
  98.     }
  100.     public static void main(String[] args) {
  101.         Elevator e = new Elevator();
  102.         while (e.currentFloor &gt;= 0) {
  103.             e.request();
  104.             if (e.currentFloor &gt;= 0) {
  105.                 e.passenger();
  106.             }
  107.         }
  108.     }
  109. }

huangapple
  • 本文由 发表于 2020年10月24日 16:17:38
  • 转载请务必保留本文链接：https://go.coder-hub.com/64511354.html
  • java
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