《大话设计模式--简单工厂模式》笔记

迈不过友情╰ 2022-04-17 05:47 208阅读 0赞

***简单工厂模式***  
需要谁，就是生产谁。  
书中计算器例子，java代码实现。  
1、首先是一个运算类，他有两个number属性，主要用于保存计算的前后数，然后有一个抽象方法gerResult()，用于得到结果，加减乘除都写成了运算类的子类。继承他后重写gerResult()方法，这样如果想要修改其中一个算法都不再需要提供其他方法的代码，提高代码的安全性。  
2、创建OperationFactory工厂类，通过输入的运算符号来判断调用哪一个算法。

3、运算类

//运算类
    public abstract class Operation {
    
    	// 输入的数字A
    	protected double numberA = 0;
    	// 输入的数字B
    	protected double numberB = 0;
    
    	// AB的运算结果
    	public abstract double getResult() throws Exception;
    
    	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;
    	}
    
    }

4、加减乘除子类

public class OperationAdd extends Operation {
    
    	@Override
    	public double getResult() {
    		
    		double result =0;
    		
    		result=getNumberA()+getNumberB();
    		
    		return result;
    	}
    
    }

public class OperationSub extends Operation {
    
    	@Override
    	public double getResult() {
    
    		double result = 0;
    
    		result = getNumberA() - getNumberB();
    
    		return result;
    	}
    
    }

public class OperationMul extends Operation {
    
    	@Override
    	public double getResult() {
    
    		double result = 0;
    
    		result = getNumberA() * getNumberB();
    
    		return result;
    	}
    
    }

public class OperationDiv extends Operation {
    
    	@Override
    	public double getResult() throws Exception {
    
    		double result = 0;
    		if (getNumberB() == 0) {
    			throw new Exception("除数不能为零.");
    		}
    
    		result = getNumberA() / getNumberB();
    
    		return result;
    	}
    }

5、运算工厂类

public class OperationFactory {
    
    	public static Operation createOperation(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;
    
    	}
    
    }

6、调用计算器程序

public class DoOperation {
    
    	public static void main(String[] args) {
    		Operation oper = null;
    
    		oper = OperationFactory.createOperation("/");
    
    		oper.setNumberA(4);
    		oper.setNumberB(2);
    
    		double result = 0;
    		try {
    			result = oper.getResult();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    
    		System.out.println(result);
    	}
    
    }