设计模式-简单的工厂模式

之前了解一些设计模式，只是粗略的了解到设计模式的名称，对各种设计模式并不懂。听闻说大话设计模式这本书不错，近来下载其电子版以学之，初读第一章，无事以记之。

  对于一个简单的计算器我们该如何设计，能达到面向对象的特点，达到最优的设计。面向对象的设计思想，通过封装、继承、多态把程序的耦合度降低，用设计模式使程序更加的灵活，容易修改，并且易于复用。计算器设计结构图如下：

 

用java实现代码如下：

 

运算类

public class Operation {  private double numberA; private double numberB;  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() throws Exception {  return 0; }}

 

 

加减乘除类

public class OperationAdd extends Operation {  public double getResult() {    return getNumberA() + getNumberB(); }}

 

 

public class OperationSub extends Operation {

 public double getResult() {    return getNumberA() - getNumberB(); }}

 

public class OperationMul extends Operation {

 public double getResult() {    return getNumberA() * getNumberB(); }}

 

 

public class OperationDiv extends Operation {

 public double getResult() throws Exception {    if (getNumberB() == 0)  {   throw new Exception("除数不能为零");  }  return getNumberA() / getNumberB(); }}

 

简单的工厂类

public class OperationFactory {

 public static Operation createOperate(char operate) {  Operation op = null;  switch (operate)  {  case '+':   op = new OperationAdd();   break;     case '-':   op = new OperationSub();   break;     case '*':   op = new OperationMul();   break;     case '/':   op = new OperationDiv();   break;      }    return op; }}

测试类，简单客户端了，呵呵

public class Calculator {

 public static void main(String[] args) {  Operation op;  op = OperationFactory.createOperate('+');  op.setNumberA(1);  op.setNumberB(2);  double result;  try {   result = op.getResult();   System.out.print(result);  } catch (Exception e) {   // TODO Auto-generated catch block   e.printStackTrace();  } }}

以后就是我学习工厂模式的一点笔记，有错的地方，请大家指正。