简单工厂模式

介绍

使用一个单独的类去实现创建实例的过程。实现要操作类和实际操作类的解耦，增加程序可扩展性。

使用

public class SimpleFactory {
    public static void main(String[] args) {
        Operation operation = OperationFactory.createOperation("+");
        operation.setNumberA(1);
        operation.setNumberB(4);
        System.out.println(operation.getResult());
    }
}
/**
 * 抽象操作类
 */
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();
}
/**
 * 加法操作
 */
class OperationAdd extends Operation{

    @Override
    public double getResult() {
        return getNumberA() + getNumberB();
    }
}
/**
 * 减法操作
 */
class OperationSub extends Operation{

    @Override
    public double getResult() {
        return getNumberA() - getNumberB();
    }
}
/**
 * 乘法操作
 */
class OperationMul extends Operation{

    @Override
    public double getResult() {
        return getNumberA() * getNumberB();
    }
}
/**
 * 除法操作
 */
class OperationDiv extends Operation{

    @Override
    public double getResult() {
        if (getNumberB() == 0){
            try {
                throw new Exception("除数不能为0");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return getNumberA() / getNumberB();
    }
}
/**
 * 操作工厂类
 */
class OperationFactory{
    public static Operation createOperation(String operation){
        if (operation.equals("+")){
            return new OperationAdd();
        } else if (operation.equals("-")){
            return new OperationSub();
        } else if (operation.equals("*")){
            return new OperationMul();
        } else {
            return new OperationDiv();
        }
    }
}