简单工厂模式

简单工厂模式实现计算器

计算类代码：

public abstract class Count {private double a = 0 ;private double b = 0 ;public double getB() {return b;}public void setB(double b) {this.b = b;}public double getA() {return a;}public void setA(double a) {this.a = a;}abstract double GetResult() throws Exception;}

编写子类，具体的计算方法，继承计算类：

class Countadd extends Count{@Overridedouble GetResult() {// TODO Auto-generated method stubdouble result = 0 ;result = getA() + getB();return result;}}class Countsub extends Count{@Overridedouble GetResult() {// TODO Auto-generated method stubdouble result = 0 ;result = getA() - getB();return result;}}

这里只给出加法和减法的例子。现在的问题是不知道实例化哪个对象，这里就用到工厂模式，将来如果想增加其他的运算，乘法除法开根平方就很容易了。

编写工厂类：

public class CountFactory {public static Count createCount(String value){Count cou = null;switch (value) {case "+":cou = new Countadd();break;case "-":cou = new Countsub();break;}return cou;}}

这时只输入符号工厂类会实例化出适合的对象，通过多态，返回父类的方法实现计算结果。

更改时，只需添加方法比如Countsub（乘法类），再添加到工厂类的case中。

main方法：

public class jisuanqi {@SuppressWarnings("resource")public static void main(String[] args){try {System.out.print("first number:");Scanner a1 = new Scanner(System.in);double a = a1.nextDouble();System.out.print("value:");Scanner c1 = new Scanner(System.in);String c = c1.next();System.out.print("second number:");Scanner b1 = new Scanner(System.in);double b = b1.nextDouble();Count cou;cou = CountFactory.createCount(c);cou.setA(a);cou.setB(b);System.out.println("result:"+cou.GetResult());} catch (Exception e) {System.out.println("error:"+e.getMessage());} }}

笔记：

scanner sc = new scanner(System.in);

String x = sc.nextLine();