（二十二）設計模式-簡單工廠模式

1、定義

用一個單獨的類來做這個創造實例的過程，這就是工廠。

2、使用場景

加減乘除運算封裝

3、代碼結構UML圖

簡單工廠類：實例工廠類；
運算類：運算操作抽象類；
加、減、乘、除法類：具體的運算類。

4、類的實現

（1）、Operation（運算抽象類）

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（工廠類）

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（具體運算類）

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、客戶端調用

 public static void main(String[] args) {

        Operation oper = OperationFactory.createOperate("+");
        oper.setNumberA(1);
        oper.setNumberB(1);
        double result = oper.getResult();
        System.out.println("輸出結果：" + result);
    }

輸出：

6、總結

工廠模式比較簡單，主要是實例集中創建，採用靜態方法調用。

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參考：《大話設計模式》