。如果用户输入了无效的重量或年龄，程序应该立即显示错误消息并结束程序，则我的程序在输入完成后会显示错误消息

Question

。在输入年龄和体重后，我的程序会显示一条错误消息。谁能帮我？例如：用户为switch语句输入1以选择输入月份的年龄和以kg为单位的重量。如果用户在几个月内输入-5，则应立即显示错误消息并结束程序。相反，我的程序所做的是在-5岁之后输入年龄，它会提示用户输入体重。在输入重量之后，它会给我提供错误信息并结束我的程序。任何帮助都感激不尽。

import java.util.Scanner; 
import java.lang.Math; 
public class infant{ 

public static void main(String[] args) { 
Scanner sc = new Scanner(System.in); 
int number; 
double ageMonths = 0; 
double ageYears = 0; 
double weightPounds = 0; 
double weightKg = 0; 


System.out.println("Choice 1 input the age in months, then weight in kilograms");   // this tells the user what the numbers 1-4 does when chosen 
System.out.println("Choice 2 input the age in years, weight in kilograms"); 
System.out.println("Choice 3 input the age in months, weight in pounds"); 
System.out.println("Choice 4 input the age in years, weight in pounds"); 


number =sc.nextInt(); 

if(number<=4 && number>=1){             // if statement that makes the user enter a value from 1 to 4 for the switch statment. 
     System.out.println("valid number selection"); 
    }else{ System.out.println("need to choose a number between 1 and 4"); 
     return; 
    } 

switch(number){                 // switch statment that allows the user to choose how they want to enter the height and weight 
    case 1: System.out.println("age in months: "); ageMonths =sc.nextDouble(); 
      System.out.println("weight in kilograms: "); weightKg =sc.nextDouble(); 
      ageYears = ageMonths * 0.0833334;           // this switch statment also converts Kg to pounds and years to months in order for math equation in the if statement at then end of the program to work. 
      weightPounds = weightKg * 2.20462; 
      break; 
    case 2: System.out.println("age in years: "); ageYears =sc.nextDouble(); 
      System.out.println("weight in kilograms: "); weightKg =sc.nextDouble(); 
      ageMonths = ageYears * 12; 
      weightPounds = weightKg * 2.20462; 
      break; 
    case 3: System.out.println("age in months: "); ageMonths =sc.nextDouble(); 
      System.out.println("weight in pounds: "); weightPounds =sc.nextDouble(); 
      ageYears = ageMonths * 0.0833334; 
      weightKg = weightPounds * 0.453592; 
      break; 
    case 4: System.out.println("age in years: "); ageYears =sc.nextDouble(); 
      System.out.println("weight in pounds: "); weightPounds =sc.nextDouble(); 
      ageMonths = ageYears * 12; 
      weightKg = weightPounds * 0.453592; 
      break; 
    default: System.out.println("you entered in an invalid number"); 

}  

if(ageMonths<=24 && ageMonths>-0.1){          // if statement that makes sure the ages are in the correct range 
    System.out.println("valid age input"); 
    }else if(ageYears>-0.1 && ageYears<=2){ 
     System.out.println("valid age input"); 
    }else{ System.out.println("You entered a invaild age 0 to 24 months only"); 
     return; 
} 

    if(weightPounds>=4.40925 && weightPounds<=33.0693 || weightKg>=2 && weightKg<=15){  // if statement that makes sure the weight are in the correct range 
     System.out.println("valid weight input"); 
    }else{ System.out.println("You entered a invaild weight 2kg to 15kg only"); 
     return; 
    } 




    if(weightKg >= ageYears * ageMonths/3 + 2 && weightKg <= 5 * ageYears * ageMonths/12 + 5){ // if statement that does a math equation to determine if your infant is healthy or not 
     System.out.println(" your infant is healthy"); 
    }else{ System.out.println(" your infant is not healthy"); 
    } 

    } 
    } 

Answer 1

检查权和几个月的代码，你保持代码的无论是在一些不同的功能，然后将开关盒内你已经进入了几个月后，再打电话与月功能输入，然后你可以为重量做同样的事情，这样你就可以拥有一个你想要的结构。不要问你是否需要任何澄清。

function checkMonths(double ageMonths){ 
if(ageMonths<=24 && ageMonths>-0.1){          // if statement that makes sure the ages are in the correct range 
System.out.println("valid age input"); 
}else{ System.out.println("You entered a invaild age 0 to 24 months only"); 
    return; 
} 
} 
function checkYears(double ageYears){ 
if(ageYears>-0.1 && ageYears<=2){ 
    System.out.println("valid age input"); 
}else{ System.out.println("You entered a invaild age 0 to 24 months only"); 
    return; 
} 
} 


function checkWeights(double weightPounds){ 

if(weightPounds>=4.40925 && weightPounds<=33.0693 || weightKg>=2 && weightKg<=15){  // if statement that makes sure the weight are in the correct range 
    System.out.println("valid weight input"); 
}else{ System.out.println("You entered a invaild weight 2kg to 15kg only"); 
    return; 
} 

} 

请根据您的使用情况更改函数参数中的变量名称。

Answer 2

如果你真的只想用无效输入结束你的程序，你总是可以使用System.exit（0）而不是“return”。这保证了程序结束。

例如：

if(number<=4 && number>=1){             // if statement that makes the user enter a value from 1 to 4 for the switch statment. 
    System.out.println("valid number selection"); 
}else{ System.out.println("need to choose a number between 1 and 4"); 
    System.exit(0); 
} 

除非我记错了，应该立即打印语句后终止主线程。