java设计模式之---简单工厂模式

1、简单工厂模式属于创建型模式，又叫做静态工厂方法。简单工厂模式是由一个工厂对象决定创建出哪一种产品类的实例。

2、测试代码分类：

　　（1）工厂角色：OperationFactory

　　（2）抽象产品角色：Operation

　　（3）具体产品角色：OperationAdd、OperationSub

3、代码：

　　运算类：

public class Operation {

    private double numA = 0;
    private double numB = 0;

    public double getNumA() {
        return numA;
    }

    public void setNumA(double numA) {
        this.numA = numA;
    }

    public double getNumB() {
        return numB;
    }

    public void setNumB(double numB) {
        this.numB = numB;
    }

    public double getResult () {
        return 0;
    }

}
　　工厂类：

public class OperationFactory {

    public static Operation createOperation (String operate) {
        Operation operation = null;
        switch (operate) {
            case "+":
            {
                operation = new OperationAdd();
                break;
            }
            case "-":
            {
                operation = new OperationSub();
                break;
            }
        }
        return operation;
    }
}
　　具体实现类--加法：

public class OperationAdd extends Operation {

    @Override
    public double getResult() {
        return getNumA()+getNumB();
    }
}
　　具体实现类--减法：

public class OperationSub extends Operation {

    @Override
    public double getResult() {
        return getNumA() - getNumB();
    }
}
　　测试入口：

public class OperateTest {

    public static void main(String[] args) {
        Operation operation = OperationFactory.createOperation("+");
        operation.setNumA(2);
        operation.setNumB(3);
        System.out.println(operation.getResult());

        Operation operation1 = OperationFactory.createOperation("-");
        operation1.setNumA(3);
        operation1.setNumB(1);
        System.out.println(operation1.getResult());

    }

}
　　输出结果：

　　5.0
　　2.0