当我运行程序时,它会运行 else 部分并执行,但在 if 部分它只会继续循环并且不会停止,直到我必须强行停止它。我正在尝试为其提供从 1 到 4 的选择参数以及不低于 1 的米参数。除了参数之外还有其他选择吗?
import java.util.*;
public class Project4
{
public static void showKilometers(double meters) //this is a parameterized function
{
double kilometers = meters * 0.001;
System.out.println(meters +" meters is " + kilometers + " kilometers.");
}
public static void showInches(double meters)
{
double inches = meters * 39.37;
System.out.println(meters +" meters is " + inches + " inches.");
}
public static void showFeet(double meters)
{
double feet = meters * 3.281;
System.out.println(meters +" meters is " + feet + " feet.");
}
public static void quitProgram()
{
System.out.println("Goodbye!");
System.out.println(0);
}
public static void showMenu()
{
System.out.println(" 1. Convert to kilometers ");
System.out.println(" 2. Convert to inches ");
System.out.println(" 3. Convert to feet ");
System.out.println(" 4. Quit the program ");
System.out.println(" ");
}
public static void main (String [] args)
{
double meters;
int choice;
Scanner keyboard = new Scanner (System.in);
System.out.println("Enter a distance in meters: ");
meters = keyboard.nextDouble();
while (meters <=0 || meters > 0)
{
if (meters > 0)
{
showMenu();
meters = keyboard.nextDouble();
}
else
{
System.out.println("Please enter a number greater than 1");
meters = keyboard.nextDouble();
showMenu();
}
}
choice = keyboard.nextInt();
switch(choice) //note the use of switch case
{
case 1: showKilometers(meters);
break;
case 2:showInches(meters);
break;
case 3:showFeet(meters);
break;
case 4:
quitProgram();
}
}
}
最佳答案
这是一个无限循环。你不妨写while (true)
尝试 while (meters <= 0)
或while (meters >0)
或者:
Scanner keyboard = new Scanner (System.in);
System.out.println("Enter a distance in meters: ");
meters = keyboard.nextDouble();
while (meters < 1 || meters.isNaN())
{
System.out.println("Please enter a number greater than 1");
meters = keyboard.nextDouble();
showMenu();
}
您的输出还指定“大于 1”,因此您的条件需要一致。
关于java - 这个java程序中的while循环有什么问题?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13434042/