策略模式定义了一系列算法，并将每个算法封装起来，使他们可以相互替换，且算法的变化不会影响到使用算法的客户。需要设计一个接口，为一系列实现类提供统一的方法，多个实现类实现该接口，设计一个抽象类（可有可无，属于辅助类），提供辅助函数，关系图如下：
java版:
package com.shuang.strategy;
public class AbstractCalculator {
public int[] split(String exp,String opt){
String array[]=exp.split(opt);
int arrayInt[]=new int[2];
arrayInt[0]=Integer.parseInt(array[0]);
arrayInt[1]=Integer.parseInt(array[1]);
return arrayInt;
}
}
package com.shuang.strategy;
public interface ICalculator {
public int calculate(String exp);
}
package com.shuang.strategy;
public class Minus extends AbstractCalculator implements ICalculator{
@Override
public int calculate(String exp) {
int arrayInt[]=split(exp, "-");
return arrayInt[0]-arrayInt[1];
}
}
package com.shuang.strategy;
public class Plus extends AbstractCalculator implements ICalculator{
@Override
public int calculate(String exp) {
int arrayInt[]=split(exp, "\\+");
return arrayInt[0]+arrayInt[1];
}
}
package com.shuang.strategy;
public class StrategyTest {
public static void main(String[] args) {
String exp="2+8";
ICalculator calculator=new Plus();
int result=calculator.calculate(exp);
System.out.println(result);
}
}
c++版：
#include<iostream>
using namespace std;
class Strategy
{
public:
virtual void crypt()=0;
};
class AES:public Strategy
{
public:
virtual void crypt()
{
cout<<"AES加密算法"<<endl;
}
};
class DES:public Strategy
{
public:
virtual void crypt()
{
cout<<"DES加密算法"<<endl;
}
};
class Context
{
public:
void setStragegy(Strategy *strategy)
{
this->strategy=strategy;
}
void myoperator()
{
strategy->crypt();
}
private:
Strategy *strategy;
};
int main()
{
Strategy *strategy=NULL;
strategy=new DES;
Context *context=new Context;
context->setStragegy(strategy);
context->myoperator();
delete strategy;
delete context;
system("pause");
return 0;
}