Question

我正在尝试为明信片制作一个类和一个单独的打印机类。我们的想法是制作一张明信片，可以为发件人，收件人和场合提供用户输入。然后添加一些允许我们将同一张明信片发送给另一位朋友的东西。这是我的明信片类

public class Postcard
    { 
      private String message;
      //define other variables that you need in this class
      private String sender;
      private String recipiant;
      private String occasion;
      private String print;
      // Methods go here
      public Postcard()
      {
          String message = "Happy holidays too ";
          String sender = "Michael";
          String recipiant = "";
          String occasion = "";
      }
      public void setmessage(String m)
      {
          this.message = m;
      }
      public void setSender(String s)
      {
          this.sender = s;
      }
      public void setRecipiant(String r)
      {
          this.recipiant = r;
      }
      public void setOccasion(String o)
      {
          this.occasion = o;
      }
      public String print()
     {
          print = message + sender + recipiant + occasion;
          return print;
     }
}

这是明信片印刷类

import java.util.Scanner;
public class PostcardPrinter
{
   public static void main(String[] args)
   {
      String text = "Happy Holiday to ";//write your msg here
      Postcard myPostcard = new Postcard(); // use the constructor method
      //use the mutator method to set the name of the recipient
      Scanner op = new Scanner(System.in);
      String recipant = op.nextLine();
      String sender = op.nextLine();
      String occassion = op.nextLine();


      myPostcard.print();

      //write the code to send the same msg to another friend
      System.out.println("Do you want to send another? Type 'yes' or 'no' ");
      String choice = op.nextLine();
      while (choice != no)
      {   
        String text = "Happy Holiday to ";
        Postcard myPostcard = new Postcard(); 
        Scanner op = new Scanner(System.in);
        String recipant = op.nextLine();
        String sender = op.nextLine();
        String occassion = op.nextLine();
      }
   } 
   }

错误出现在while循环中，表示varriable no不存在，当注释掉时，没有任何反应。虚拟机正在运行，但没有任何反应。任何帮助将不胜感激

Answer 1

该行：

while (choice != no)

正在寻找名为no的变量，而不是字符串常量。你想要：

while (!choice.equals("no"))

或者，不区分大小写的方法：

while (!choice.equalsIgnoreCase("no"))

有一点需要指出 - 因为choice的值在循环内部永远不会改变，所以你基本上会永远循环。在循环的每次迭代之后，您可能希望再次询问。您可以将 choice 的初始值设置为空字符串，然后在程序开始时立即启动循环。这将允许您删除循环上方的冗余代码。

Java明信片类和打印机

1 个答案: