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java - Java if/else 语句

问题描述

我正在计算机类中完成我的最终项目，并尝试在嵌套类中实现基本的 if/else 语句，但它只选择使用 else 情况。导入 java.util.Scanner；

public class CollegeApplication {

   public static void main(String[] args) {

       Scanner scan = new Scanner(System.in);

       //create object by default constructor
       College c1 = new College();
       //create object by overloaded constructor
       College c2 = new College("Frostburg", "Frostburg", "MD", 5142);
       College c3 = new College("UMBC", "Baltimore", "MD", 14000);
       //set the information of object 1
       c1.setName("Full Sail");
       c1.setCity("Winter Park");
       c1.setState("FL");
       c1.setStudent_Body(19285);

       System.out.println("Enter your states two-letter abbreviation");
       String user_State = scan.nextLine();

       c1.printCollege();
       System.out.println();
       c2.printCollege();
       System.out.println();
       c3.printCollege();
   }
}
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import java.util.Scanner;

public class College {

   // private data members
   private String name;
   private String city;
   private String state;
   private int student_Body;
   private String tuition;
   private String user_State;

   // default constructor which set the data member to default value
   public College() {

       this.name = "";
       this.city = "";
       this.state = "";
       this.student_Body = 0;
       this.tuition = "";
       this.user_State = "";
   }

   // parameterized constructor
   public College(String name, String city, String state, int student_Body) {
       super();
       this.name = name;
       this.city = city;
       this.state = state;
       this.student_Body = student_Body;
   }

   // getter and setter
   public String getName() {
       return name;
   }

   public void setName(String name) {
       this.name = name;
   }

   public String getCity() {
       return city;
   }

   public void setCity(String city) {
       this.city = city;
   }

   public String getState() {
      return state;
   }

   public void setState(String state) {
      this.state = state;  
   }

   public int getStudent_Body() {
       return student_Body;
   }

   public void setStudent_Body(int student_Body) {
       this.student_Body = student_Body;
   }    
   // print college data
   public void printCollege() {

       System.out.println("Name of College: " + name);
       System.out.println("City of Collge: " + city);
       System.out.println("State of Collge: " + state);
       System.out.println("Student Body Count: " + student_Body);

   this.user_State = user_State;
      if (state.equals(user_State)) {
         this.tuition = "Eligible";
      }
      else {
         this.tuition = "Ineligible";
      }

       System.out.println("In-State Tuition: " + tuition); 
   }
}

如果有人可以帮助 id 知道如何更改 if 语句以不仅打印不合格，我将不胜感激

标签： javaclassif-statementsuperclass

解决方案

这个问题不包含问题，但我看到了问题区域。

问问自己为什么你College同时拥有 astate和 a user_State。为什么这个类本身的一个方面是 user_State？甚至没有 getter 和 setter （因为不应该有）。

public void printCollege() {

   this.user_State = user_State;
      if (state.equals(user_State)) {
         this.tuition = "Eligible";
      }
      else {
         this.tuition = "Ineligible";
      }

       System.out.println("In-State Tuition: " + tuition); 
   }

此函数不接受输入也不提供输出，但具有打印某些内容和修改字段的副作用。

唯一一次引用 user_State 是College当它设置为空字符串时。

this.user_State = "";

仅当College使用默认构造函数构造对象时。如果College使用参数构造函数创建对象，则user_State保留null.

无论如何，此方法首先将这个空字符串（或 null）设置为自身：

this.user_State = user_State;

所以它只是空字符串（或null）。

接下来，它将字符串state与空字符串或 null in进行比较user_State。

if (state.equals(user_State)) {

state在您的任何测试用例中都不等于空字符串或 null，因此它继续到 else 子句：

else {
    this.tuition = "Ineligible";
}

您可能打算printCollege()采用user_State您向用户询问的变量。在这种情况下，它不需要 0 个参数，它需要 1 个字符串参数。

public void printCollege(String userState) {

      if (state.equals(userState)) {
         this.tuition = "Eligible";
      }
      else {
         this.tuition = "Ineligible";
      }

       System.out.println("In-State Tuition: " + tuition); 
   }

printCollege(String userState)并且应该根据您从用户那里收到的输入来适当地调用。

以后请遵循 Java 命名约定，例如user_State应该是userState.

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