java 计算器基于工厂模式和功能单一模式

import java.util.Scanner;

public class CaculationTest {

    public static void main(String[] args) {

        Scanner reader = new Scanner(System.in);
        double a, b, result = 0;
        String operator;
        Operation operation = null;

        System.out.println("************************");
        System.out.println("*   学号：1308060310    *");
        System.out.println("*   班级：网络131班      *");
        System.out.println("*   姓名：王朝远         *");
        System.out.println("************************");

        TwoFromConsole twoFromConsole = new TwoFromConsole();
        a = twoFromConsole.getFirstDoubleFromConsole(); // 获取第一个数
        b = twoFromConsole.getTwoDoubleFromConsole(); // 获取第二个数

        OperatorFromConsole operatorFromConsole = new OperatorFromConsole();
        operator = operatorFromConsole.getOperator(); // 获取运算符号
        do {
            if (operator.equals("/") && b == 0) {
                System.out.print("除法运算分母不能为0，请重新输入,");
                b = twoFromConsole.getTwoDoubleFromConsole(); // 获取第二个数
                continue;
            }
            break;
        } while (true);

        // 获取要运算的对象
        operation = Factory.getInstance(operator);
        result = operation.getResult(a, b);

        // 判断用户是否继续对数运算，如果是继续对数运算，结果的输出方式就不一样,并且让用户选择是否再次计算
        if (operator.equals("log")) {

            System.out.println("log" + "(" + b + ")" + a + "=" + result);
        } else {
            System.out.println(a + operator + b + "=" + result);
        }
    }
}

class TwoFromConsole {

    Scanner reader = new Scanner(System.in);

    // 获取数字的方法的具体实现
    public double getFirstDoubleFromConsole() {

        double x = 0;
        System.out.print("请输入第一个数字：");
        do {
            double temp = 0;
            try {
                temp = reader.nextDouble();
            } catch (Exception e) {
                System.out.print("请重新输入第一个数字：");
                continue;
            }
            x = temp;
            break;
        } while (true);
        return x;
    }

    public double getTwoDoubleFromConsole() {

        double x = 0;
        System.out.print("请输入第二个数字：");
        do {
            double temp = 0;
            try {
                temp = reader.nextDouble();
            } catch (Exception e) {
                System.out.print("请重新输入第二个数字：");
                continue;
            }
            x = temp;
            break;
        } while (true);
        return x;
    }
}

/**
 * 获取运算符类
 */
class OperatorFromConsole {

    Scanner reader = new Scanner(System.in);

    /**
     * @return 合理的运算符
     */
    public String getOperator() {
        System.out.print("请输入运算符：");

        String operator;
        boolean b;
        do {
            operator = reader.nextLine();
            b = !(operator.equals("+") || operator.equals("-") || operator.equals("*") || operator.equals("/")
                    || operator.equals("log"));
            if (b == true) {
                System.out.print("请重新输入运算符：");
            }
        } while (b);

        return operator;
    }
}

/**
 * 功能：各个运算的父接口，子类必须实现父接口里面的方法
 */
interface Operation {

    double getResult(double x, double y);
}

/**
 * 实现加法运算的类
 */
class Add implements Operation {

    /**
     * 重写接口里面的方法，并实现加法功能
     */
    @Override
    public double getResult(double x, double y) {
        // TODO Auto-generated method stub
        return x + y;
    }

}

/**
 * 实现减法运算的类
 */
class Sub implements Operation {

    /**
     * 重写接口里面的方法，并实现减法功能
     */
    @Override
    public double getResult(double x, double y) {
        // TODO Auto-generated method stub
        return x - y;
    }
}

/**
 * 实现乘法运算的类
 */
class Mul implements Operation {

    /**
     * 重写接口里面的方法，并实现乘法功能
     */
    @Override
    public double getResult(double x, double y) {
        // TODO Auto-generated method stub
        return x * y;
    }

}

/**
 * 实现除法运算的类
 */
class Div implements Operation {

    /**
     * 重写接口里面的方法，并实现除法功能
     */
    @Override
    public double getResult(double x, double y) {
        // TODO Auto-generated method stub
        return x / y;
    }

}

/**
 * 实现对数运算的类
 */
class Logarithm implements Operation {

    /**
     * 重写接口里面的方法，并实现对数运算功能
     */
    @Override
    public double getResult(double x, double y) {
        // TODO Auto-generated method stub
        return Math.log(x) / Math.log(y); // x表示对数，y表示底数
    }

}

/**
 * 生成用户所需要的对象工厂类
 */
class Factory {

    /**
     * @param operator
     *            用户选择的运算
     * @return 用户所需要的对象
     */
    public static Operation getInstance(String operator) {
        Operation operation = null;
        switch (operator) {
        case "+":
            operation = new Add(); // 实例化加法对象
            break;
        case "-":
            operation = new Sub(); // 实例化减法对象
            break;
        case "*":
            operation = new Mul(); // 实例化乘法对象
            break;
        case "/":
            operation = new Div(); // 实例化除法对象
            break;
        case "log":
            operation = new Logarithm(); // 实例化对数运算对象
            break;
        }

        return operation;
    }
}