第四讲：工厂模式在开发中的运用

运用面向对象的思想将加法运算封装起来.

如果不希望  Operation operation = new AddOperation();   new一个Operation那就使用简单工厂模式.

以下就是使用了简单工厂模式之后直接从工厂类里面获取AddOperation.

Operation operation = OperationFactory.getOperation(oper);
operation.setNum1(num1);
operation.setNum2(num2);
result = operation.getResult();

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要添加的话直接在工厂类里面添加判断和添加操作类.这样程序拥有了扩展性.你可以无限扩展.符合了开放封闭原则中的开放原则.那么现在是封闭的吗?它不是封闭的,因为现在添加操作的话工厂类也是要修改的.

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那么现在使用工厂方法模式,把工厂类抽象出来,把具体的操作交给它的子类(具体工厂类).

所以工厂方法模式在客户端里面必须进行判断, 这就是简单工厂模式和工厂方法模式在计算器这个例子中的应用.

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在面试中写出简单工厂模式即可,工厂方法模式并不强求.可以应用更高级的技术:反射来动态加载哪个类.

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public abstract class Operation {
    private double num1;
    private double num2;
    public double getNum1() {
        return num1;
    }
    public void setNum1(double num1) {
        this.num1 = num1;
    }
    public double getNum2() {
        return num2;
    }
    public void setNum2(double num2) {
        this.num2 = num2;
    }
    public abstract double getResult();
}

public class AddOperation extends Operation {

    @Override
    public double getResult() {
        // TODO Auto-generated method stub
        double result = this.getNum1() + this.getNum2();
        return result;
    }

}

/*public class OperationFactory {
     public static Operation getOperation(String oper){
         if("+".equals(oper)){
             return new AddOperation();
         }else if ("-".equals(oper)){
             return new SubtractionOperation();
         }
        return null;
         
     }
     }
     */
public interface OperationFactory{
    //public Operation getOperation(String oper);
    public Operation getOperation();
}

public class AddOperationFactory implements OperationFactory{

    @Override
    //public Operation getOperation(String oper) {
        public Operation getOperation() {
        // TODO Auto-generated method stub
        return new AddOperation();
    }

}

public class SubtractionOperation extends Operation{

    @Override
    public double getResult() {
        // TODO Auto-generated method stub
        //return this.getNum1()-this.getNum2();
        double result =  this.getNum1()-this.getNum2();
        return result;
    }

}

import java.util.Scanner;


public class MainClass {
    public static void main(String[] args) {
        
    
      //1.接收控制台输入
      System.out.println("-----计算机程序-----------");
      System.out.println("输入第一个操作数");
      Scanner scanner = new  Scanner(System.in);
      String strNum1 = scanner.nextLine();
      
      System.out.println("输入运算符");
      String oper = scanner.nextLine();
      
      System.out.println("输入第二个操作数");
      String strNum2 = scanner.nextLine();
      double result = 0;
      double num1 = Double.parseDouble(strNum1);
      double num2 = Double.parseDouble(strNum2);
      //2.进行运算
/*      if("+".equals(oper)){
          //result = Double.parseDouble(strNum1) + Double.parseDouble(strNum2);
          Operation operation = new AddOperation();
          operation.setNum1(num1);
          operation.setNum2(num2);
          result = operation.getResult();
      } else if("-".equals(oper)){
          result = Double.parseDouble(strNum1) - Double.parseDouble(strNum2);
      } else if("*".equals(oper)){
          result = Double.parseDouble(strNum1) * Double.parseDouble(strNum2);
      } else if("/".equals(oper)){
          result = Double.parseDouble(strNum1) / Double.parseDouble(strNum2);
      }*/
    
      /*Operation operation = OperationFactory.getOperation(oper);
      operation.setNum1(num1);
      operation.setNum2(num2);
      result = operation.getResult();
      */
      if("+".equals(oper)){
          OperationFactory factory = new AddOperationFactory();
          Operation operation = factory.getOperation();
          operation.setNum1(num1);
          operation.setNum2(num2);
          result = operation.getResult();
      }
      //3.返回结果
      System.out.println(strNum1 + oper + strNum2 + "=" +result);
      
}
}