java度量衡换算器

以下是一个Java度量衡换算器的例子，它可以将长度、重量和温度单位进行转换：

import java.util.Scanner;

public class UnitConverter {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int choice = 0;
        while (choice != 4) {
            System.out.println("请选择要转换的单位类型：");
            System.out.println("1.长度");
            System.out.println("2.重量");
            System.out.println("3.温度");
            System.out.println("4.退出");
            choice = input.nextInt();
            switch (choice) {
                case 1:
                    lengthConverter();
                    break;
                case 2:
                    weightConverter();
                    break;
                case 3:
                    temperatureConverter();
                    break;
                case 4:
                    System.out.println("感谢使用本换算器！");
                    break;
                default:
                    System.out.println("无效的选择，请重新输入！");
                    break;
            }
        }
    }

    public static void lengthConverter() {
        Scanner input = new Scanner(System.in);
        double value;
        String fromUnit, toUnit;
        System.out.println("请输入要转换的数值：");
        value = input.nextDouble();
        System.out.println("请输入要转换的单位：");
        fromUnit = input.next();
        System.out.println("请输入要转换成的单位：");
        toUnit = input.next();
        double result = 0;
        if (fromUnit.equals("m")) {
            if (toUnit.equals("cm")) {
                result = value * 100;
            } else if (toUnit.equals("km")) {
                result = value / 1000;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("cm")) {
            if (toUnit.equals("m")) {
                result = value / 100;
            } else if (toUnit.equals("km")) {
                result = value / 100000;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("km")) {
            if (toUnit.equals("m")) {
                result = value * 1000;
            } else if (toUnit.equals("cm")) {
                result = value * 100000;
            } else {
                result = value;
            }
        } else {
            System.out.println("无效的单位！");
            return;
        }
        System.out.println(value + fromUnit + " = " + result + toUnit);
    }

    public static void weightConverter() {
        Scanner input = new Scanner(System.in);        double value;
        String fromUnit, toUnit;
        System.out.println("请输入要转换的数值：");
        value = input.nextDouble();
        System.out.println("请输入要转换的单位：");
        fromUnit = input.next();
        System.out.println("请输入要转换成的单位：");
        toUnit = input.next();
        double result = 0;
        if (fromUnit.equals("kg")) {
            if (toUnit.equals("g")) {
                result = value * 1000;
            } else if (toUnit.equals("lb")) {
                result = value * 2.20462;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("g")) {
            if (toUnit.equals("kg")) {
                result = value / 1000;
            } else if (toUnit.equals("lb")) {
                result = value * 0.00220462;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("lb")) {
            if (toUnit.equals("kg")) {
                result = value / 2.20462;
            } else if (toUnit.equals("g")) {
                result = value / 0.00220462;
            } else {
                result = value;
            }
        } else {
            System.out.println("无效的单位！");
            return;
        }
        System.out.println(value + fromUnit + " = " + result + toUnit);
    }

    public static void temperatureConverter() {
        Scanner input = new Scanner(System.in);
        double value;
        String fromUnit, toUnit;
        System.out.println("请输入要转换的数值：");
        value = input.nextDouble();
        System.out.println("请输入要转换的单位：");
        fromUnit = input.next();
        System.out.println("请输入要转换成的单位：");
        toUnit = input.next();
        double result = 0;
        if (fromUnit.equals("C")) {
            if (toUnit.equals("F")) {
                result = value * 9 / 5 + 32;
            } else if (toUnit.equals("K")) {
                result = value + 273.15;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("F")) {
            if (toUnit.equals("C")) {
                result = (value - 32) * 5 / 9;
            } else if (toUnit.equals("K")) {
                result = (value + 459.67) * 5 / 9;
            } else {
                result = value;
            }
        } else if (fromUnit.equals("K")) {
            if (toUnit.equals("C")) {
                result = value - 273.15;
            } else if (toUnit.equals("F")) {
                result = value * 9 / 5 - 459.67;
            } else {
                result = value;
            }
        } else {
            System.out.println("无效的单位！");
            return;
        }
        System.out.println(value + fromUnit + " = " + result + toUnit);
    }
}