java输入验证: how can I split the user input at the space?

Question

我的任务:

Perform input validation by making sure that the user enters a positive integer number for feet, a nonnegative decimal number for inches, and a positive decimal number for weight. See the sample session for details. In particular, note the format for the echo-printed height and weight values and for the generated body-mass-index value.

我的程序可以运行，但我不知道如何使它看起来像下面的示例程序。我必须让用户输入以英尺为单位的高度，然后输入空间，然后输入英寸。我不知道如何在空间中分割用户输入。

示例 session :

Enter height using feet space inches (e.g., 5 6.25): hi there
Invalid feet value. Must be an integer.
Invalid inches value. Must be a decimal number.
Re-enter height using feet space inches (e.g., 5 6.25): 0 9
Invalid feet value. Must be positive.
Re-enter height using feet space inches (e.g., 5 6.25): 5.25 0
Invalid feet value. Must be an integer.
Re-enter height using feet space inches (e.g., 5 6.25): 5 9.25
Enter weight in pounds: 0
Invalid pounds value. Must be positive.
Re-enter weight in pounds: 150.5
height = 5'-9.25"
weight = 150.5 pounds
body mass index = 22.1

到目前为止我的代码:

package ch14;
import java.util.Scanner;

public class BMI {


public static void main(String[] args) {

    String inputString;
    double bmi;
    double pounds;
    double inches;
    String feet;

    Scanner stdIn = new Scanner(System.in);

    System.out.print("Please enter height using feet space inches (e.g., 5 6.25): ");
    inputString = stdIn.nextLine();


    try
    {
        Double.parseDouble(inputString);
    }
    catch(NumberFormatException nfe)
    {
        System.out.println ("Invalid inch value. Number must be a decimal.");
        System.out.print ("Re-enter height in inches: ");
        inputString = stdIn.nextLine ();
    }

    inches=Double.parseDouble(inputString);

    if(inches<=0)
    {
        System.out.println("Invalid inch value. Must be a positive number.");
        System.out.print("Re-enter height in inches:");
        inputString = stdIn.nextLine();
        inches=Double.parseDouble(inputString);
    }

    System.out.print("enter weight(in pounds) ");
    inputString = stdIn.nextLine();

    try
    {
        Double.parseDouble(inputString);
    }
    catch(NumberFormatException nfe)
    {
        System.out.println("Invalid pound value. Number must be a decimal.");
        System.out.print("Re-enter the weight in pounds: ");
        inputString = stdIn.nextLine();
    }

    pounds=Double.parseDouble(inputString);

    if(pounds <= 0)
    {
        System.out.println("Invalid pound value. Must be a positive number.");
        System.out.print("Re-enter the weight in pounds:");
        inputString = stdIn.nextLine();
        pounds=Double.parseDouble(inputString);
    }

    System.out.println("Height = " + inches + "\"");
    System.out.println("Weight = " + pounds + " pounds");
    System.out.printf("Body Mass Index = %.1f\n",(pounds * 703.)/(inches * inches));

    }//end main
}

Answer 1

您使用 .split 进行拆分所以，对于一个空间...

mystring.split("\\s");

对于任意数量的空格...

mystring.split("\\s+");

这两个操作都会返回一个字符串数组，然后可以像任何其他数组一样访问该数组...

String mystring = "Hello World";
String[] words = mystring.split("\\s");
System.out.println(words[0]); //<--- Would print "Hello"

对于您的特定问题，您可能希望将这些 String 对象转换为 Double 或其他对象。您可以使用 Double.parseDouble() 来完成此操作。例如，

Double number = Double.parseDouble("1.0");

上面这行代码将 "1.0" String 对象转换为 double 值 1.0。