設計模式： 簡單工廠模式

使用簡單工廠模式封裝對象的創建過程。這裏以加減乘除計算爲例。

代碼

Operation運算類

父類

package simple.service;

public abstract class Operation {
    protected double numberA;
    protected double numberB;
    public abstract double getResult();

    public void setNumberA(double numberA) {
        this.numberA = numberA;
    }

    public void setNumberB(double numberB) {
        this.numberB = numberB;
    }
}

public class OperationAdd extends Operation {
    public double getResult() {
        return this.numberA+this.numberB;
    }
}

public class OperationDiv extends Operation {
    public double getResult() {
        return this.numberA/this.numberB;
    }
}

public class OperationMul extends Operation {
    public double getResult() {
        return this.numberA * this.numberB;
    }
}

public class OperationSub extends Operation {
    public double getResult() {
        return this.numberA-this.numberB;
    }
}

工廠類

使用工廠類創建對象

public class OperatorFactory {

    public static Operation createOperate(String operateStr){
        Operation operation = null;

        switch (operateStr)
        {
            case "+": {
                operation = new OperationAdd();
                break;
            }
            case  "-": {
                operation = new OperationSub();
                break;
            }
            case "*": {
                operation = new OperationMul();
                break;
            }
            case "/": {
                operation = new OperationDiv();
                break;
            }
        }
        return operation;
    }
}

客戶端

public class Client {

    public static void main(String[] args) {
        Operation operation = OperatorFactory.createOperate("+");
        operation.setNumberA(1.0);
        operation.setNumberB(4.0);
        System.out.println(operation.getResult());
    }

}

特點

簡單工廠模式可以屏蔽實現過程。但是如果需要擴展運算類的話，需要修改工廠類。這不符合OOP的開閉原則。