簡單工廠模式

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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
//Operation運算類
public abstract class Operation {

    private double _numberA = 0;
    private double _numberB = 0;

    public void setNumberA(double a) {
        _numberA = a;
    }

    public void setNumberB(double b) {
        _numberB = b;
    }

    public double getNumberA() {
        return _numberA;
    }

    public double getNumberB() {
        return _numberB;
    }
    
    public abstract double gerResult();
}

Operation

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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
//加法類
class OperationAdd extends Operation {

    @Override
    public double gerResult() {
        double result = 0;
        result = getNumberA() + getNumberB();
        return result;
    }
}

OperationAdd

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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
//減法類
class OperationSub extends Operation {
    @Override
    public double gerResult() {
        double result = 0;
        result = this.getNumberA() - this.getNumberB();
        return result;
    }
}

OperationSub.java

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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
class OperationMul extends Operation {

    @Override
    public double gerResult() {
        double result = 0;
        result = this.getNumberA() * this.getNumberB();
        return result;
    }
}

OperationMul.java

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package simpleFactory;
/**
 *
 * @author XiaoTianCai
 */
class OperationDiv extends Operation {

    @Override
    public double gerResult() {
        double result = 0;
        try {
            result = this.getNumberA() / this.getNumberB();
        } catch (Exception ex) {
            System.out.println("除數不能爲0.");
        }
        return result;
    }
}

OperationDiv.java

/*
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 * and open the template in the editor.
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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
//簡單運算工廠類
public class OperationFactory {
    public static Operation createOperate(String operate)
    {
        Operation oper=null;
        switch(operate)
        {
            case "+":
                oper=new OperationAdd();
                break;
            case "-":
                oper=new OperationSub();
                break;
            case "*":
                oper=new OperationMul();
                break;
            case "/":
                oper=new OperationDiv();
                break;
        }
        return oper;
    }   
}

OperationFactory.java

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package simpleFactory;

/**
 *
 * @author XiaoTianCai
 */
public class mainTest {

    public static void main(String[] args) {
        Operation oper;
        /*
         只須要輸入運算符號，工廠就實例化出合適的對象，聽過多態，返回父類的方式實現計算結果
         */
        oper = OperationFactory.createOperate("/"); //實例化對象
        oper.setNumberA(12);
        oper.setNumberB(0);

        double result = oper.gerResult();
        System.out.println(result);
    }
}

mainTest .java