【设计模式】简单工厂模式

        简单工厂模式又称静态工厂方法模式，不属于GOF设计模式。是由一个工厂对象决定创建出哪一种产品类的实例。优点在于只需要特定的输入就可以利用工厂类的静态方法实例化出合适的对象，缺点在于容易违反高内聚责任分配原则。

        以计算器实例为例进行实践，本篇代码简化为由Console输出进行模拟。

        目标类：

package chapter1;

/**
 * @author CHK
 * This class is used to define Operation.
 *
 */
public abstract class Operation {
	private double numberA = 0;
	private double numberB = 0;
	
	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 abstract double getResult();
}

class OperationAdd extends Operation {
	@Override
	public double getResult() {
		return this.getNumberA() + this.getNumberB();
	}
}

class OperationSub extends Operation {
	@Override
	public double getResult() {
		return this.getNumberA() - this.getNumberB();
	}
}

class OperationMul extends Operation {
	@Override
	public double getResult() {
		return this.getNumberA() * this.getNumberB();
	}
}

class OperationDiv extends Operation {
	@Override
	public double getResult(){
		return this.getNumberA() / this.getNumberB();
	}
}

        工厂类：

package chapter1;

/**
 * @author CHK
 * This class is used to generate target Operation.
 *
 */
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;
	}
}

        测试类：

package chapter1;

/**
 * @author CHK
 * This class is used to test OperationFactory.
 *
 */
public class FactoryTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Operation oper;
		oper = OperationFactory.createOperate("+");
		oper.setNumberA(1);
		oper.setNumberB(2);
		System.out.println(oper.getResult());
	}

}