java设计模式之简单工厂模式

Z时代
2024-01-10
分类：IT

在编写一个计算器程序时，可以将业务逻辑和显示分离，业务逻辑封装为一个类（封装）；如果要新添加一种运算，可以先创建一个Operation的基类，然后各种运算从Operation类继承，并实现GetResult()虚函数，这时添加新的运算只需要派生一个新的类，即不需要之前的运算参与编译。如何让计算器知道我是希望使用哪种运算呢？应该考虑单独的类来做这个创造实例的过程，这就是工厂。创建一个OperationFactory类，传入参数，函数createOperate就可以实例化出合适的对象。

Java代码如下：


public class OperationFactory {
 public static abstract class Operation
 {  
  private double _numberA = 0;
  private double _numberB = 0;
  public double get_numberA() {
   return _numberA;
  }
  public void set_numberA(double _numberA) {
   this._numberA = _numberA;
  }
  public double get_numberB() {
   return _numberB;
  }
  public void set_numberB(double _numberB) {
   this._numberB = _numberB;
  }
  abstract double GetResult();
  // TODO Auto-generated constructor stub
 }
 public static class OperationAdd extends Operation
 {
  double GetResult() 
  {
   double result = get_numberA() + get_numberB();
   return result;
  }  
 }
 public static class OperationSub extends Operation
 {
  double GetResult() {
   double result = get_numberA() - get_numberB();
   return result; 
  }
 }
 public static Operation createOperate(String operate){
  Operation oper = null;
  if (operate.equals("+")) {
   oper = new OperationAdd();
  }
  else if (operate.equals("-")) {
   oper = new OperationSub();
  }
  return oper;
 }
 public static void main(String[] args) {
  Operation oper;
  oper = OperationFactory.createOperate("+");
  oper.set_numberA(1);
  oper.set_numberB(2);
  double result = oper.GetResult();
 }
}