1.简单工厂模式

类图：

 

这个是《大话设计模式》中简单工厂的例子。

代码如下：

Operation:运算类

public class Operating {
	
	private double firstNum;
	private double secondNum;
	private double result;
	public double getResult() {
		return result;
	}
	public void setResult(double result) {
		this.result = result;
	}
	public double getFirstNum() {
		return firstNum;
	}
	public void setFirstNum(double firstNum) {
		this.firstNum = firstNum;
	}
	public double getSecondNum() {
		return secondNum;
	}
	public void setSecondNum(double secondNum) {
		this.secondNum = secondNum;
	}
	

}

 OperatingAdd：加法类

package 简单计算器;

public class OperatingAdd extends Operating {

	public double getResult(){
		double result = 0;
		result = getFirstNum() + getSecondNum();
		return result;
	}
	
}

OperatingSub:减法类

package 简单计算器;

public class OperatingSub extends Operating {
	
	public double getResult(){
		double result = 0;
		result = getFirstNum() - getSecondNum();
		return result;
	}
}

OperationMul：乘法类

package 简单计算器;

public class OperatingMul extends Operating {
	
	public double getResult(){
		double result = 0;
		result = getFirstNum() * getSecondNum();
		return result;
	}
}

OperationDiv:除法类

package 简单计算器;

public class OperatingDiv extends Operating{

	public double getResult(){
		double result = 0;
		try{
			result = getFirstNum() / getSecondNum();
		}catch(Exception e){
			System.out.println("除数不能为0！");
		}
		
		return result;
	}
	
}

OperationFactory:简单工厂类

package 简单计算器;

public class OperatingFactory {
	
	public static Operating createOperate(String operate){
		Operating oper = null;
		
		switch(operate)
		{
		case "+":
			oper =  new OperatingAdd();
			break;
		case "-":
			oper = new OperatingSub();
			break;
		case "*":
			oper = new OperatingMul();
			break;
		case "/":
			oper = new OperatingDiv();
			break;
		}
		return oper;
		
	}

}

运行类：

package 简单计算器;

public class Run {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Operating oper;
		oper = new OperatingFactory().createOperate("/");
		oper.setFirstNum(3);
		oper.setSecondNum(0);
		System.out.println(oper.getResult());
	}

}