定义：它定义了算法家族，分别封装起来，让它们之间可以相互替换，此模式让算法的变化，不会影响到使用算法的客户

结构图：

示例代码：

public interface Strategy {

	public void algorithnInterface();
}
public class ConcreteStrategyA implements Strategy {

	@Override
	public void algorithnInterface() {
		// TODO Auto-generated method stub
		System.out.println("算法A实现");
	}

}
public class ConcreteStrategyB implements Strategy {

	@Override
	public void algorithnInterface() {
		// TODO Auto-generated method stub
		System.out.println("算法B实现");
	}

}
public class ConcreteStrategyC implements Strategy {

	@Override
	public void algorithnInterface() {
		// TODO Auto-generated method stub
		System.out.println("算法C实现");
	}

}
public class Context {

	private Strategy strategy;

	public Context(Strategy strategy) {
		this.strategy = strategy;
	}
	
	public void contextInterface() {
		
		strategy.algorithnInterface();
	}
}

public class Client {

	public static void main(String[] args) {
		
		Context context = null;
		context = new Context(new ConcreteStrategyA());
		context.contextInterface();
		
		context = new Context(new ConcreteStrategyB());
		context.contextInterface();
		
		context = new Context(new ConcreteStrategyC());
		context.contextInterface();
	}
}

运行输出：

算法A实现

算法B实现

算法C实现

设计模式之策略模式