java - Java 新手 - If - Else If 问题

Question

我刚刚开始学习 Java 并且完全被这段代码难住了。我环顾四周，但语言知识的一部分是知道要问的正确问题，而且我已经没有搜索的想法了。在我看来一切都很好，但我希望更有经验的人能够在这方面对我进行一些教育。

每当我运行此代码或单步执行时，温度从 100 到 213(无论摄氏或华氏)，Else If 将始终运行。谁能告诉我为什么会这样，或者让我进入正确的心态？这是代码:

package chapter.pkg3;

import java.util.Scanner;

public class Chapter3 {

public static void main(String[] args) {

    Scanner in = new Scanner(System.in);
    System.out.print("Please enter the temperature: ");
         double temp = in.nextDouble();
    System.out.print("Please enter the temperature measurement, C or F: ");
         String measure = in.next();
     if (measure.equals("C"))
        { measure = "Celsius";}
     else 
        {measure = "Fahrenheit";}
     if ((temp <= 0 && measure.equals("C")) || (temp <= 32 && !measure.equals("C")))
        {
        System.out.print("The temperature is " + temp + " " + measure + ".  The water
        is freezing!");
        }
     if ((temp <= 100 && measure.equals("C")) || (temp <= 212 && !measure.equals("C")))
        {
        System.out.print("The temperature is " + temp +  " " + measure + ".  The water
        is liquid.");
        }
     if ((temp > 100 && measure.equals("C")) || (temp > 212 && !measure.equals("C")))
        {
        System.out.print("At " + temp + " " + measure + " the water has become gas.");
        }
  }

在此先感谢您的帮助!

Answer 1

在你的if类似 temp <= 0 && measure.equals("C") 的条件条件measure.equals("C")永远是false因为你覆盖变量measure的值这里:

if (measure.equals("C"))
   {measure = "Celsius";}
else 
   {measure = "Fahrenheit";}