工厂模式

工厂模式：定义一个用于创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延迟到其子类。

工厂模式和简单工厂模式的区别：
简单工厂模式的最大优点在于工厂类中包含了必要的逻辑判断，根据使用者的选择条件动态实例化相关的类，对于使用者来说，去除了与具体产品的依赖。但其违背了开放-封闭原则。

工厂模式实现时，使用者需要决定实例化哪一个工厂来实现运算类，选择判断的问题还是存在的，也就是说，工厂模式把简单工厂的内部逻辑判断移到了使用者代码来进行，你想要加功能，本来是改工厂类，而现在是修改使用类。

package com.jshx.factory;

import com.jshx.operation.Operation;

/**
 * 工厂接口
 * @author duanpf
 *
 */
public interface IFactory {
	Operation CreateOperation();
}

package com.jshx.factory;

import com.jshx.operation.Operation;
import com.jshx.operation.OperationAdd;

/**
 * 加法类工厂
 * @author duanpf
 *
 */
public class AddFactory implements IFactory {

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

}

package com.jshx.factory;

import com.jshx.operation.Operation;
import com.jshx.operation.OperationSub;

/**
 * 减法类工厂
 * @author duanpf
 *
 */
public class SubFactory implements IFactory {

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

}

package com.jshx.factory;

import com.jshx.operation.Operation;
import com.jshx.operation.OperationSub;

/**
 * 减法类工厂
 * @author duanpf
 *
 */
public class SubFactory implements IFactory {

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

}

package com.jshx.factory;

import com.jshx.operation.Operation;
import com.jshx.operation.OperationDiv;

/**
 * 除法类工厂
 * @author duanpf
 *
 */
public class DivFactory implements IFactory {

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

}

package com.jshx.factory;

import com.jshx.operation.Operation;

public class FactoryTest {
	public static void main(String[] args) throws Exception {
		IFactory operFactory = new AddFactory();
		Operation oper = operFactory.CreateOperation();
		oper.setNumberA(1);
		oper.setNumberB(2);
		double result = oper.getResult();
		System.out.println(result);
	}
}