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;

     }

 }