设计模式--简单工厂模式

从设计模式的类型上来说，简单工厂模式是属于创建型模式，又叫做静态工厂方法（StaticFactory Method）模式，但不属于23种GOF设计模式之一。简单工厂模式是由一个工厂对象决定创建出哪一种产品类的实例。简单工厂模式是工厂模式家族中最简单实用的模式，可以理解为是不同工厂模式的一个特殊实现。

 

实例：面向对象编程实现两个数的四则运算

 

运算父类：Operation.java

package factory;

public abstract class Operation {
	
	public abstract double getResult();
	
	
	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;
	}


	protected double numberA = 0;
	protected double numberB = 0;
}

运算子类：OperationAdd.java

 

package factory;

public class OperationAdd extends Operation {

	@Override
	public double getResult() {
		// TODO Auto-generated method stub
		return numberA + numberB;
	}

}

 

运算子类：OperationSub.java

 

package factory;

public class OperationSub extends Operation {

	@Override
	public double getResult() {
		// TODO Auto-generated method stub
		return numberA - numberB;
	}

}

 

 

运算子类：OperationMul.java

 

package factory;

public class OperationMul extends Operation {

	@Override
	public double getResult() {
		// TODO Auto-generated method stub
		return numberA * numberB;
	}

}

 

 

运算子类：OperationDiv.java

 

package factory;

public class OperationDiv extends Operation {

	@Override
	public double getResult() {
		// TODO Auto-generated method stub
		double result = 0;
		try {
			result = numberA / numberB;
		} catch (ArithmeticException e) {
			System.out.println("除数不能为0");
		}
		return result;
	}

}

 

工厂类：OperationFactory.java

 

package factory;

public class OperationFactory {
	public static Operation createOperation(String operator) {
		Operation operation = null;
		
		if (operator.equals("+")) {
			operation = new OperationAdd();
		} else if (operator.equals("-")) {
			operation = new OperationSub();
		} else if (operator.equals("*")) {
			operation = new OperationMul();
		} else if (operator.equals("/")) {
			operation = new OperationDiv();
		}
		
		return operation;
	}
}

 

Main函数

 

package factory;

import java.util.Scanner;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner(System.in);
		double numberA;
		double numberB;
		String operator;
		try {
			System.out.println("请输入数字A：");
			numberA = in.nextDouble();
			System.out.println("请输入运算符合(+、-、*、/)：");
			operator = in.next();
			System.out.println("请输入数字B：");
			numberB = in.nextDouble();
			
			Operation operation = OperationFactory.createOperation(operator);
			operation.setNumberA(numberA);
			operation.setNumberB(numberB);
			System.out.println("结果是：" + operation.getResult());
		} catch (Exception e) {
			System.out.println("输入错误：" + e.getMessage());
		}
	}

}