设计模式学习笔记——简单工厂模式

UML类图：

Java版代码：

abstract class Operation {
    private double numberA;
    private double numberB;

    public double getNumberA() {
        return numberA;
    }

    public void setNumberA(double numberA) {
        this.numberA = numberA;
    }

    public double getNumberB() {
        return numberB;
    }

    public void setNumberB(double numberB) {
        this.numberB = numberB;
    }

    public abstract double GetResult();

}

class OperationAdd extends Operation {
    @Override
    public double GetResult() {
        // TODO Auto-generated method stub
        double result = 0;
        result = getNumberA() + getNumberB();
        return result;
    }
}

class OperationSub extends Operation{
    @Override
    public double GetResult() {
        // TODO Auto-generated method stub
        double result=0;
        result=getNumberA()-getNumberB();
        return result;
    }
}

class OperationMul extends Operation{
    @Override
    public double GetResult() {
        // TODO Auto-generated method stub
        double result=0;
        result=getNumberA()*getNumberB();
        return result;
    }
}

class operationDiv extends Operation{
    @Override
    public double GetResult() {
        // TODO Auto-generated method stub
        double result=0;
        if(getNumberB()==0){
            System.out.println("除数不能为零！");
        }else{
            result=getNumberA()/getNumberB();
        }
        return result;
    }
}

class OperationFactory{
    public static Operation createOperate(String operate){
        Operation oper=null;
        switch(operate){
        case "+":
            oper=new OperationAdd();
            break;
        case "-":
            oper=new OperationSub();
            break;
        case "*":
            oper=new OperationMul();
            break;
        case "/":
            oper=new operationDiv();
            break;
        }
        return oper;
    }
}
public class SimpleFactory{
    public static void main(String[] args){
        Operation oper;
        oper =OperationFactory.createOperate("+");
        oper.setNumberA(1);
        oper.setNumberB(2);
        double result=oper.GetResult();
        System.out.println(result);
    }
}

总结：

这里的工厂类OperationFactory不是与具体的运算类相关联，而是与抽象运算类相关联，这样就降低了耦合度，即使要扩展或修改也不需要大范围的修改代码，

增强了代码的可维护性和可扩展性。