java - if...elseif 一次又一次输入值时出错

Question

虽然在这个程序中，我必须在一个循环中一次又一次地输入温度。当我输入温度后显示正确时，但是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();
        }
    }
}

Answer 1

这是因为您不在循环中。你在顶部问一次温度。然后偶尔一次，然后就结束了。

public static void main(String [] args) 
{
    final double TEMPERATURE = 102.5;
    double thermostat;
    Scanner keyboard = new Scanner(System.in);

    while (true) {
        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. ");
        }
        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 ");
        }
    }
}

小心，while 永远不会停止，但您可以根据需要更改条件。