抽象 工廠模式的本質：簡單工廠模式+反射，通過反射，將 簡單工廠模式中的switch case 去除，如果有新的演算法，

只需要 新增新的演算法類和配置檔案 即可

直接看程式碼把，之前學過 簡單工廠模式 就好理解了

/**
 * 基類  加 減 成  除 的共性
 * */
public class OperationA {
  private Double numberA;
  private Double numberB;
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 result(Double numberA,Double numberB){
	  double result=0;
	return result;
  }
  
//  abstract double result(Double numberA,Double numberB);
}
 

public class Add extends OperationA{
	
	 public double result(Double numberA,Double numberB){
		  double result=0;
		  result=numberA+numberB;
		  System.out.println(result);
		return result;
	  }
}

public class Div extends OperationA{
	public double result(Double numberA,Double numberB){
		  double result=0;
		  if (numberB!=0) {
			  result=numberA/numberB;
			  System.out.println(result);
		}else {
			System.out.println("除數不能為0");
		}
		  
		return result;
	  }
}
 

public class Sub extends OperationA{
	public double result(Double numberA,Double numberB){
		  double result=0;
		  result=numberA-numberB;
		  System.out.println(result);
		return result;
	  }
}

和簡單工廠模式不同之處

1.配置 檔案：jisuan.properties

add=shejimoshi.jiandangongchang.Add
sub=shejimoshi.jiandangongchang.Sub
div=shejimoshi.jiandangongchang.Div
 

2.讀取配置類

/**
 * 二。讀取配置類
 * */
public class ReaderProperties {

	public Map<String, String> getPropertyAndKey() {

		Map<String, String> map = new HashMap<String, String>();

		Properties pt = new Properties();

		try {

			// 讀取對映檔案

			InputStream in = getClass().getResourceAsStream("jisuan.properties");

			// 從輸入流讀取屬性列表（鍵和元素對）

			pt.load(in);

			// 返回屬性列表所有鍵的列舉

			Enumeration<?> en = pt.propertyNames();

			// 逐行讀取列舉的key和value並存放在map中

			while (en.hasMoreElements()) {

				String key = (String) en.nextElement();

				String value = pt.getProperty(key);

				map.put(key, value);
				System.out.println(map.get(key));
				System.out.println(map.get(value));

			}

		} catch (Exception e) {

			e.printStackTrace();

		}

		return map;

	}

}

3.工廠類

/**
 * 三。計算工廠類
 * */
public class JiSuanFactory {

	public static OperationA getOperation(String key) {
//		獲取jisuan.properties檔案屬性列表
		Map<String, String> propertyAndKey = new ReaderProperties().getPropertyAndKey();
//		通過對映找到對應得類
		try {
			OperationA newInstance = (OperationA) Class.forName(propertyAndKey.get(key)).newInstance();
			return newInstance;
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
		
	}
}

4.客戶端

/**
 * 客戶端
 * */
public class Test4 {
public static void main(String[] args) {
//	 建立工廠
	JiSuanFactory jiSuanFactory = new JiSuanFactory();
//	具體得操作
	jiSuanFactory.getOperation("add").result(3.3, 3.3);
}
}