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;
     }
 }