設計模式|第一篇:簡單工廠模式

1. 概念

簡單工廠模式:創建對象工廠(用於生產對象)，根據傳入條件返回不同的對象

2.案例

本案例以計算器爲例，主要實現邏輯有如下幾步:

​1.根據用戶傳入的運算符，獲取所需要的運算對象
2.根據獲得的運算對像調用計算方法

• 創建計算對象父類

  public interface Arithmetic {
  
    double calute(double arg1,double arg2);
  
  }
  

• 創建各計算對象子類

  //加法
  public class Plus implements Arithmetic {
  
      @Override
      public double calute(double arg1, double arg2) {
          return arg1 + arg2;
      }
  }
  //減法
  public class Substruction implements Arithmetic {
  
    @Override
    public double calute(double arg1, double arg2) {
      return arg1 - arg2;
    }
  }
  //乘法
  public class Multiplication implements Arithmetic {
  
    @Override
    public double calute(double arg1, double arg2) {
      return arg1 * arg2;
    }
  }
  //除法
  public class Division implements Arithmetic {
  
    @Override
    public double calute(double arg1, double arg2) {
      if (0==arg2){
        throw new RuntimeException("除數不能爲0");
      }
      return arg1 / arg2;
    }
  }
  

• 創建計算對象工廠,根據條件返回不同的對象

  public class ArithmeticFactory {
  
    public static Arithmetic getArithmetic(String operator){
      switch (operator){
        case "+":
          return new Plus();
        case "-":
          return new Substruction();
        case "*":
          return new Multiplication();
        case "/":
          return new Division();
        default:
          throw new RuntimeException("輸入運算符有誤");
      }
    }
  }
  

• 驗證

  public class MainTest {
  
    public static void main(String[] args) {
      Arithmetic plus = ArithmeticFactory.getArithmetic("+");
      double calute = plus.calute(1, 2);
      System.out.println(calute);
  
      Arithmetic division = ArithmeticFactory.getArithmetic("/");
      calute = division.calute(1, 0);
      System.out.println(calute);
  
    }
  }
  
  

• 案例結構

  爲了方便理解，如下爲本案例結構圖: