《大话设计模式》--简单工厂模式

题目：用java实现一个简单的计算器功能（用户从控制台输入）计算两个数和一个运算符号

public class Optioner {
    private int numFirst;
    private int numSecond;

    public int getNumFirst() {
        return numFirst;
    }

    public void setNumFirst(int numFirst) {
        this.numFirst = numFirst;
    }

    public int getNumSecond() {
        return numSecond;
    }

    public void setNumSecond(int numSecond) {
        this.numSecond = numSecond;
    }

    public Optioner() {
    }

    public Optioner(int numFirst, int numSecond) {
        this.numFirst = numFirst;
        this.numSecond = numSecond;
    }

    public int getResult() {
        return 0;
    }
}

public class AddOptioner extends Optioner {
    @Override
    public int getResult() {
        return getNumFirst() + getNumSecond();
    }
}

public class SubOptioner extends Optioner {
    @Override
    public int getResult() {
        return getNumFirst() - getNumSecond();
    }
}

public class MulOptioner extends Optioner {
    @Override
    public int getResult() {
        return getNumFirst() * getNumSecond();
    }
}

public class DivOptioner extends Optioner {
    @Override
    public int getResult() {
        if (getNumSecond() == 0) {
            System.out.println("除数不能为0");
            return -1;
        } else {
            return getNumFirst() / getNumSecond();
        }
    }
}

public class OptionerFactory {
    public static Optioner createOptioner(String opt) {
        Optioner optioner = null;
        switch (opt) {
            case "+":
                optioner = new AddOptioner();
                break;
            case "-":
                optioner = new SubOptioner();
                break;
            case "*":
                optioner = new MulOptioner();
                break;
            case "/":
                optioner = new DivOptioner();
                break;
        }
        return optioner;
    }
}

public class Test {
    public static void main(String args[]) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入第一个数：");
        int numFirst = scanner.nextInt();
        System.out.print("请输入操作方式(+,-,*,/):");
        String opt = scanner.next();
        System.out.print("请输入第二个数:");
        int numSecond = scanner.nextInt();
        Optioner optioner = OptionerFactory.createOptioner(opt);
        optioner.setNumFirst(numFirst);
        optioner.setNumSecond(numSecond);
        System.out.println("结果为：" + optioner.getResult());
    }
}

Optioner是父类，根据情况不同，通过OptionerFactory工厂得到对应的实际操作类

Optioner封装了两个参数和操作符，加减乘除类继承了Optioner，OptionerFactory中多态得到了对应的加减乘除类。

加减乘除独自成类是为了拓展更多的操作运算，然后只要在工厂类中加判断条件即可，其他类不用动