简单工厂

本文根据大话设计模式写

什么是简单工厂？

我的理解就是通过一个if-else、swich或者其他的操作，来判断一个操作调用一个借口/抽象类等的哪一个具体的实现类。

Demo 简单计算器实现：

这个Demo通过OperationFactory创建出Operation运算类的具体子类，实现计算器的功能。

OperationFactory就是一个生产具体运算子类的简单工厂。

/**
 * @说明：运算类父类
 * 
 * */
public class Operation {
	protected double numberA = 0;
	protected 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 double getResult() {
		double result = 0;
		return result;
	}

}

/**
 * @说明：加法运算
 * 
 * */
public class OperationAdd extends Operation {
  @Override
	public double getResult(){
	   double result=0;
	   result=numberA+numberB;
	   return result;
   }
}
/**
 * @说明：减法运算
 * 
 * */
public class OperationSub extends Operation {
	@Override
	public double getResult() {
		double result = 0;
		result = numberA - numberB;
		return result;
	}
}
/**
 * @说明：乘法运算
 * 
 * */
public class OperationMul extends Operation {
	@Override
	public double getResult() {
		double result = 0;
		result = numberA * numberB;
		return result;
	}
}


/**
 * @说明：除法运算
 * 
 * */
public class OperationDiv extends Operation {
	@Override
	public double getResult() {
		double result = 0;
		result = numberA / numberB;
		return result;
	}
}

/**
 * @说明：简单工厂，根据传入的运算符，来确定调用那个Operation的具体子类。
 * 
 * */
public class OperationFactory {
	public static Operation createOperate(String operate) {
		Operation oper = null;
		OperateType operateType = OperateType.getOperateType(operate);
		switch (operateType) {
		case ADD:
			oper = new OperationAdd();
			break;
		case SUBTRACT:
			oper = new OperationSub();
			break;
		case MULTIPLY:
			oper = new OperationMul();
			break;
		case DIVIDE:
			oper = new OperationDiv();
			break;
		default:
			break;
		}
		return oper;
	}
}

/**
 * @author mengfei1001
 * @说明：计算器运算符枚举
 *
 * */
public enum OperateType {
	ADD("+"), SUBTRACT("-"), MULTIPLY("*"), DIVIDE("/");
	private String value;

	private OperateType(String value) {
		this.value = value;

	}

	public static OperateType getOperateType(String type) {
		if (type == null) {
			return OperateType.ADD;
		}
		for (OperateType t : OperateType.values()) {
			if (t.value.equals(type)) {
				return t;
			}
		}
		return OperateType.ADD;
	}

	public String getValue() {
		return value;
	}

	public void setValue(String value) {
		this.value = value;
	}

}

/**
 * @说明：测试类
 * 
 * */
public class Test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("请输入数字A：");
		double numberA = sc.nextDouble();
		System.out.println("请选择运算符号(+、-、*、/):");
		String operate = sc.next();
		System.out.println("请输入数字B：");
		double numberB = sc.nextDouble();
		Operation oper = OperationFactory.createOperate(operate);
		oper.setNumberA(numberA);
		oper.setNumberB(numberB);
		double result = oper.getResult();
		System.out.println(result);
	}
}