if ... elseif一次又一次输入值时出错

问题描述

在这个程序中，我必须一次又一次地在循环中输入温度。 当我输入温度一旦它显示正确的显示，但当我再次输入温度时，程序自行终止。

代码是：

import java.util.Scanner;

public class CheckTemperature
{
    public static void main(String [] args) 
    {
        final double TEMPERATURE = 102.5;
        double thermostat;

        Scanner keyboard = new Scanner(System.in);
        System.out.println("Enter the substance's temperature: ");
        thermostat = keyboard.nextDouble();

        if(thermostat > TEMPERATURE)
        {
            System.out.print("The temperature is too high. ");
            System.out.print("Turn down the thermostat. ");
            System.out.println("Wait for 5 minutes and check the thermostat again. "); 
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }
        else if(thermostat < TEMPERATURE)
        {
            System.out.println("The temperature is low.");
            System.out.println("Turn up the thermostat.");
            System.out.println("Check for 5 minutes and check again.");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }
        else if(thermostat == TEMPERATURE)
        {
            System.out.println("The temperature is acceptable. Check again in 15 minutes.");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }
        else
        {
            System.out.println("Enter the correct temperature value ");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }
    }
}

如果你想一次又一次地获得温度，你必须使用循环。

while(true){
    if(thermostat > TEMPERATURE)
        {
            System.out.print("The temperature is too high. ");
            System.out.print("Turn down the thermostat. ");
            System.out.println("Wait for 5 minutes and check the thermostat again. "); 
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();

        }
        else if(thermostat < TEMPERATURE)
        {
            System.out.println("The temperature is low.");
            System.out.println("Turn up the thermostat.");
            System.out.println("Check for 5 minutes and check again.");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();

        }

        else if(thermostat == TEMPERATURE) {

            System.out.println("The temperature is acceptable. Check again in 15 minutes.");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }

        else{
            System.out.println("Enter the correct temperature value ");
            System.out.println("Enter the thermostat here: ");
            thermostat = keyboard.nextDouble();
        }
    }

您的代码不是为了“重复”任何AKA迭代的任务而构建的。 在代码中添加一个循环，使其根据需要重复操作。

这里我们使用while (1==1)创建一个无限循环。 此外，我们在检查input ==“X”时添加了一个退出条件，它从循环中触发System.exit 。 这有助于保持从应用程序的优雅退出，而不必强制关闭。

    final double TEMPERATURE = 102.5;
    double thermostat;
    while(true){
           Scanner keyboard = new Scanner(System.in);
           System.out.println("Enter the substance's temperature or press X to exit: ");
           String input = keyboard.next();
           if(input.equals("X")){
              System.exit(0);
           } else{
              thermostat = Double.parseDouble(input);   
              if(thermostat > TEMPERATURE) {
                    System.out.print("The temperature is too high. ");
                    System.out.print("Turn down the thermostat. ");
                    System.out.println("Wait for 5 minutes and check the thermostat again. "); 
                } else if(thermostat < TEMPERATURE) {
                    System.out.println("The temperature is low.");
                    System.out.println("Turn up the thermostat.");
                    System.out.println("Check for 5 minutes and check again.");
                } else if(thermostat == TEMPERATURE) {
                    System.out.println("The temperature is acceptable. Check again in 15 minutes.");
                } else {
                    System.out.println("Enter the correct temperature value ");
                }
           }
    }

Murtaza，你可以只使用一个循环或者可以使用任何递归方法并在你的main方法中调用它。你所谈论的双重错误的错误是由于没有像equals（）这样的方法扫描器class.besides，你不应该将int值与double类型变量进行比较。再次，要在if-else块中比较它，你应该使用Double中的equals（）方法，包装类反对传递一个对象它的参数。