設計模式-工廠方法模式

時間 2019-12-07

標籤設計模式工廠方法简体版

原文原文鏈接

　　　　本篇文章主要講解工廠方法模式。工廠方法模式：定義一個用於建立對象的接口，讓子類去決定實例化哪個類。工廠方法使一個類的實例化延遲到其子類。git

　　　　在看工廠方法模式以前先寫個簡單的計算器看下簡單工廠。github

　　　　先看下結構圖。ide

　　　　接着看下代碼實現。測試

　　　　首先建立一個運算抽象類。spa

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 運算抽象類
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:45
 */
public abstract class Operation {

    double numberA = 0;
    double numberB = 0;

    abstract double getResult();

}

　　　　而後是四種運算的實現類。code

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 加法實現類
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:47
 */
public class OperationAdd extends Operation {

    double getResult() {
        return numberA + numberB;
    }

}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 減法實現類
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:48
 */
public class OperationSub extends Operation {

    double getResult() {
        return numberA - numberB;
    }
}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 乘法實現類
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:49
 */
public class OperationMul extends Operation {

    double getResult() {
        return numberA * numberB;
    }

}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 除法實現類
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:51
 */
public class OperationDiv extends Operation {

    double getResult() {
        if (numberB == 0){
            throw new ArithmeticException("除數不能爲0");
        }
        return numberA / numberB;
    }

}

　　　　接着建立運算工廠類，根據運算符去建立對應的實現類。對象

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 運算工廠類
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:06
 */
public class OperationFactory {

    public static Operation createOperation(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;
        }
        return operation;
    }

}

　　　最後是測試類和測試結果。blog

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: lwx
 * Date: 2019-03-09
 * Time: 20:59
 */
public class OperationTest {

    public static void main(String[] args) {
        Operation operation = OperationFactory.createOperation("+");
        operation.numberA = 5;
        operation.numberB = 10;
        System.out.println(operation.getResult());
    }

}

　　　　以上就是簡單工廠的示例代碼，只須要傳入運算符號工廠類就能夠自動返回對應的計算實現類。　　　　接口

　　　　接下來把上面的計算器改爲工廠方法模式。ip

　　　　老規矩先看下結構圖。

　　　　在上面代碼的基礎上加入工廠接口類以及具體實現類，上面的運算工廠類就不用了。

　　　　先建立一個工廠接口。

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 工廠接口
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:15
 */
public interface Factory {

    Operation createOperation();

}

　　　　而後是四種運算的具體實現工廠類。

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 加法類工廠
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:16
 */
public class AddFactory implements Factory {

    @Override
    public Operation createOperation() {
        return new OperationAdd();
    }

}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 減法工廠類
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:17
 */
public class SubFactory implements Factory {

    @Override
    public Operation createOperation() {
        return new OperationSub();
    }

}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 乘法工廠類
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:18
 */
public class MulFactory implements Factory {

    @Override
    public Operation createOperation() {
        return new OperationMul();
    }

}

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description: 除法工廠類
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:19
 */
public class DivFactory implements Factory {

    @Override
    public Operation createOperation() {
        return new OperationDiv();
    }

}

　　　　最後看下工廠方法模式的測試類和運行結果。

package com.lwx.factory;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: lwx
 * Date: 2019-03-09
 * Time: 21:58
 */
public class FactoryTest {

    public static void main(String[] args) {
        Factory factory = new DivFactory();
        Operation operation = factory.createOperation();
        operation.numberA = 8;
        operation.numberB = 10;
        System.out.println(operation.getResult());
    }
    
}