循环逃跑

Question

即使while循环的条件为false，我的while循环仍会输出数据。

package temperature;

import java.util.Scanner;

public class Temperature {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double tempInput = 0, tempF = 0, counter = 0;



        while (tempInput > -100.-0) {
            System.out.println("Please enter in temperature in Centigrade");
            tempInput = scan.nextDouble();
            tempF = (9.0/5.0)*tempInput + 32.0;
            System.out.print("(F" + tempF + ")");
            System.out.print(" " + "C (" +  tempInput + ")");
            System.out.println("");
        }
    }

}

示例输出：

Please enter in temperature in Centigrade
-100
(F-148.0) C (-100.0)

更多：

Please enter in temperature in Centigrade
23
(F73.4) C (23.0)
Please enter in temperature in Centigrade
32
(F89.6) C (32.0)
Please enter in temperature in Centigrade
100
(F212.0) C (100.0)
Please enter in temperature in Centigrade

Answer 1

目前你的while循环条件是：

while (tempInput > -100.-0) { }

-100.-0的评估结果为-100。循环在tempInput < -100时停止，我运行程序并输入-101并且循环终止。

Answer 2

WHILE LOOP

当特定条件为真时，while语句会不断执行一个语句块。其语法可表示为：

while (expression) {
     statement(s)
}

你的循环将一直有效，直到给定的条件为真：

while (tempInput > -100.-0)

直到你提供tempInput的值＆gt; -100.0，如果为tempInput提供23的正值，它将检查条件为（23> -100.0），这是真的。因此循环将继续执行，直到tempInput的时间大于-100。

Answer 3

你可以写：

import java.util.Scanner;

public class Temperature {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double tempInput = 0, tempF = 0, counter = 0;



        while (true) {
            System.out.println("Please enter in temperature in Centigrade");
            tempInput = scan.nextDouble();
            if (tempInput <= -100.0) {
                break;
            }
            tempF = (9.0/5.0)*tempInput + 32.0;
            System.out.print("(F" + tempF + ")");
            System.out.print(" " + "C (" +  tempInput + ")");
            System.out.println("");
        }
    }

}

Answer 4

当您输入数据时，您将立即将其打印出来而不检查条件。如果在打印之前再做另一个。

package temperature;

import java.util.Scanner;

public class Temperature {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double tempInput = 0, tempF = 0, counter = 0;



        while (tempInput > -100.-0) {
            System.out.println("Please enter in temperature in Centigrade");
            tempInput = scan.nextDouble();
            tempF = (9.0/5.0)*tempInput + 32.0;
            if (tempInput > -100.-0) {
              System.out.print("(F" + tempF + ")");
              System.out.print(" " + "C (" +  tempInput + ")");
              System.out.println("");
            }
        }
    }
}

这里的关键概念是while条件将在循环的每次迭代开始时进行评估，而不是像一些初学者所想的那样观察变量的变化。

Answer 5

我认为您已将扫描仪输入写入错误的位置。

package temperature;


import java.util.Scanner;

public class Temperature {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double tempInput = 0, tempF = 0, counter = 0;
        System.out.println("Please enter in temperature in Centigrade");
        tempInput = scan.nextDouble();

        while (tempInput > -100. - 0) {
            tempF = (9.0 / 5.0) * tempInput + 32.0;
            System.out.print("(F" + tempF + ")");
            System.out.print(" " + "C (" + tempInput + ")");
            System.out.println("");
            break;
        }
    }

}

Answer 6

正如我所说，你必须在while循环之外定义Scanner和double变量，以确保每次迭代的值不能为每个双变量ex..tempInput = 0，tempF = 0设置为零，counter = 0;

这将有效。

Answer 7

  

添加一个用于停止循环的其他内容。

实施例

package temperature;

import java.util.Scanner;

public class Temperature {
public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double tempInput = 0, tempF = 0, counter = 0;



    while (tempInput > -100.-0) {
        System.out.println("Please enter in temperature in Centigrade");
        tempInput = scan.nextDouble();
        tempF = (9.0/5.0)*tempInput + 32.0;
        System.out.print("(F" + tempF + ")");
        System.out.print(" " + "C (" +  tempInput + ")");
        System.out.println("");
    } else {
     //Stopping the loop
   }
}

}