Java新手 - 如果 - 否则如果问题

Question

我只是在学习Java,并且完全被这些代码所困扰.我环顾四周,但语言知识的一部分是知道要问的正确问题,而且我已经没有想法去搜索了.一切看起来都不错,但我希望一个更有经验的人能够教育我一点点.

每当我执行此代码或逐步执行时,对于100到213(无论摄氏温度或华氏温度)的温度,Else If将始终运行.任何人都可以告诉我为什么会这样,或者让我进入正确的思维框架？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条件下temp <= 0 && measure.equals("C"),条件measure.equals("C")总是false因为你在这里覆盖变量的值measure:

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