我正在学习方法，并尝试制作一个简单转换的方法菜单。我不知道如何从菜单中调用方法并使其执行该功能。我想知道如何调用一个方法，并使用不使用扫描仪类的输入运行它，除了在main中。
CompositionTarget.Rendering public static void main(String[] args) {
displayMenu();
Scanner keyboard = new Scanner(System.in);
int selection = keyboard.nextInt();
switch(selection) {
case 1:
FahrToCel();
break;
case 2:
CelToFahr();
break;
case 3:
LbToKilo();
break;
case 4:
KiloToLb();
break;
}
}
public static void displayMenu() {
System.out.println("Enter 1 for Fahrenheit to Celsius" );
System.out.println("Enter 2 for Celsius to Fahrenheit");
System.out.println("Enter 3 for lb to kg");
System.out.println("Enter 4 for kg to lb");
return;
public static double FahrToCel() {
double Fahrenheit = ???;
double Celsius = 5 * (Fahrenheit - 32) / 9;
return Celsius;
}
public static double CelToFahr() {
double Celsius = ???;
double Fahrenheit = (9 * Celsius / 5) + 32;
return Fahrenheit;
}
public static double LbtoKilo() {
double pounds = ???;
double factor = 0.454;
double Kilogram = pounds * factor;
return Kilogram;
}
public static double KiloToLb() {
double kilograms = ???;
double factor = 0.454;
double Pound = kilograms / factor;
return Pound;
}
是我想要获得用户输入的变量，但是idk如何在不在每个方法中创建新的Scanner的情况下执行此操作。
idk如何获取方法中的输入。
当我运行代码时，我得到displayMenu选项，我可以输入1,2,3,4，但之后没有任何反应
答案 0 :(得分：2)
你可能想让你的代码像这样。您的问题是您实际上并没有提供任何要转换的值，但这应该解决它。
public static void main(String[] args) {
displayMenu();
double result;
Scanner keyboard = new Scanner(System.in);
int selection = keyboard.nextInt();
System.out.println("What number do you want converted?");
int toBeConverted = keyboard.nextInt();
switch(selection) {
case 1:
result = fahrToCel(toBeConverted);
break;
case 2:
result = celToFahr(toBeConverted);
break;
case 3:
result = lbToKilo(toBeConverted);
break;
case 4:
result = kiloToLb(toBeConverted);
break;
}
System.out.println(result);
}
public static void displayMenu() {
System.out.println("Enter 1 for Fahrenheit to Celsius" );
System.out.println("Enter 2 for Celsius to Fahrenheit");
System.out.println("Enter 3 for lb to kg");
System.out.println("Enter 4 for kg to lb");
return;
}
public static double fahrToCel(int fahrenheit) {
double celsius = 5 * (fahrenheit - 32) / 9;
return celsius;
}
public static double celToFahr(int celsius) {
double fahrenheit = (9 * celsius / 5) + 32;
return fahrenheit;
}
public static double lbtoKilo(int lb) {
double factor = 0.454;
double kilogram = lb * factor;
return kilogram;
}
public static double kiloToLb(int kilo) {
double factor = 0.454;
double pound = kilo / factor;
return pound;
}
我还将所有变量和方法名称都设置为小写，因为这是一个很好的编码实践。通常只有类名在传统的java实践中大写。没有实际的好处，但当然遵循惯例总是更好。
答案 1 :(得分：1)
正如@JoshKopen所说，你没有提供你想要转换的值，我的答案几乎是一样的，只是更具体一点，使用双值而不是int来获得更高的精度。
试试这个：
ID year count
a 2001 2
b 2001 3
a 2001 2
a 2001 1
a 2001 4
a 2001 0
a 2001 1
a 2001 3
a 2001 2
b 2001 3
b 2001 4
a 2001 5
b 2001 2
c 2001 3
a 2001 5
a 2001 1
c 2001 1
c 2002 2
a 2002 1
b 2002 2
c 2002 3
a 2002 2
a 2002 1
a 2002 3
a 2002 4
a 2002 3
a 2002 2
b 2002 4
b 2002 2
a 2002 1
b 2002 1
c 2002 2
a 2002 3
a 2002 4
a 2002 5
c 2002 2
a 2003 2
a 2003 1
a 2003 2
a 2003 4
c 2003 3
a 2003 2
a 2003 1
b 2003 3
a 2003 5
a 2003 3
a 2003 2
a 2003 1
a 2003 3
a 2003 2
c 2003 2
b 2003 2
b 2003 1
b 2003 4
c 2003 3
答案 2 :(得分：0)
我刚刚去了，让菜单显得格格不入：）
package com.boeing.tbng.ddm.ms;
import java.util.Scanner;
public class StackOverflow {
private static final int FACTOR_FARENHEIT = 32;
private static final double FACTOR = 0.454;
public static void main(String[] args) {
StackOverflow so = new StackOverflow();
int selection;
Scanner keyboard = new Scanner(System.in);
do{
/* request user input */
so.displayMenu();
/* read input */
selection = keyboard.nextInt();
System.out.print(selection + ") ");
/* choose path based on selection */
switch(selection) {
case 1:
so.FahrToCel(keyboard);
break;
case 2:
so.CelToFahr(keyboard);
break;
case 3:
so.LbToKilo(keyboard);
break;
case 4:
so.KiloToLb(keyboard);
break;
case 9:
System.out.println("Quitting Program...");
break;
}
}while (selection != 9);
}
private void displayMenu() {
System.out.println("");
System.out.println("===================");
System.out.println("Select an Option:");
System.out.println("1) for Fahrenheit to Celsius");
System.out.println("2) for Celsius to Fahrenheit");
System.out.println("3) for lb to kg");
System.out.println("4) for kg to lb");
System.out.println("9) to quit");
System.out.println("===================");
}
private double askForNextInput(Scanner keyboard, String unit){
System.out.println("Enter how many " + unit + " you want to convert");
double userInput = keyboard.nextDouble();
return userInput;
}
private double FahrToCel(Scanner keyboard) {
double Fahrenheit = askForNextInput(keyboard, "Farenheit");
double Celsius = 5 * (Fahrenheit - FACTOR_FARENHEIT) / 9;
System.out.println( "In Celcius, that's: " + Celsius);
return Celsius;
}
private double CelToFahr(Scanner keyboard) {
double Celsius = askForNextInput(keyboard, "Celsius");
double Fahrenheit = (9 * Celsius / 5) + FACTOR_FARENHEIT;
System.out.println( "In Fahrenheit, that's: " + Fahrenheit);
return Fahrenheit;
}
private double LbToKilo(Scanner keyboard) {
double pounds = askForNextInput(keyboard, "Pounds");
double Kilogram = pounds * FACTOR;
System.out.println( "In Kilograms, that's: " + Kilogram);
return Kilogram;
}
private double KiloToLb(Scanner keyboard) {
double kilograms = askForNextInput(keyboard, "Kilograms");
double Pound = kilograms / FACTOR;
System.out.println( "In Pounds, that's: " + Pound);
return Pound;
}
}