（二十二）设计模式-简单工厂模式

1、定义

用一个单独的类来做这个创造实例的过程，这就是工厂。

2、使用场景

加减乘除运算封装

3、代码结构UML图

简单工厂类：实例工厂类；
运算类：运算操作抽象类；
加、减、乘、除法类：具体的运算类。

4、类的实现

（1）、Operation（运算抽象类）

public class Operation {
    private double numberA = 0;
    private double numberB = 0;

    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 double getResult() {
        double result = 0;
        return result;
    }
}

（2）、OperationFactory（工厂类）

public class OperationFactory {
    public static Operation createOperate(String operate) {
        Operation operation = null;
        switch (operate) {
            case "+":
                operation = new OperationAdd();
                break;
            case "-":
                operation = new OperationSub();
                break;
            case "*":
                operation = new OperationMul();
                break;
            case "/":
                operation = new OperationDiv();
                break;
            default:
                break;
        }
        return operation;
    }
}

（3）、OperationAdd、OperationSub、OperationMul、OperationDiv（具体运算类）

public class OperationAdd extends Operation {
    @Override
    public double getResult() {

        double result = 0;
        result = getNumberA() + getNumberB();
        return result;
    }
}
public class OperationSub extends Operation {
    @Override
    public double getResult() {
        double result = 0;
        result = getNumberA() - getNumberB();
        return result;
    }
}
public class OperationMul extends Operation {
    @Override
    public double getResult() {

        double result = 0;
        result = getNumberA() * getNumberB();
        return result;
    }
}
public class OperationDiv extends Operation {
    @Override
    public double getResult() {
        double result = getNumberA() / getNumberB();
        return result;
    }
}

5、客户端调用

 public static void main(String[] args) {

        Operation oper = OperationFactory.createOperate("+");
        oper.setNumberA(1);
        oper.setNumberB(1);
        double result = oper.getResult();
        System.out.println("输出结果：" + result);
    }

输出：

6、总结

工厂模式比较简单，主要是实例集中创建，采用静态方法调用。

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参考：《大话设计模式》