策略模式

(Updated: )
设计模式

我们需要画一个图形，可选的策略就是用红色笔来画，还是绿色笔来画，或者蓝色笔来画。

首先，先定义一个策略接口：

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public interface Strategy {
    void draw(int radius, int x, int y);
}

然后我们定义具体的几个策略：

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public class RedPen implements Strategy {
    @Override
    public void draw(int radius, int x, int y) {
        System.out.println("用红色笔画图，radius:" + radius + ", x:" + x + ", y:" + y);
    }
}
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public class GreenPen implements Strategy {
    @Override
    public void draw(int radius, int x, int y) {
        System.out.println("用绿色笔画图，radius:" + radius + ", x:" + x + ", y:" + y);
    }
}
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public class BluePen implements Strategy {
    @Override
    public void draw(int radius, int x, int y) {
        System.out.println("用蓝色笔画图，radius:" + radius + ", x:" + x + ", y:" + y);
    }
}

使用策略的类：

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public class Context {
    private Strategy strategy;

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

    public void executeDraw(int radius, int x, int y) {
        strategy.draw(radius, x, y);
    }
}

客户端演示：

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public class Main {
    public static void main(String[] args) {
        Context context = new Context(new BluePen()); // 使用蓝色笔来画
        context.executeDraw(10, 0, 0);
    }
}

output：

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用蓝色笔画图，radius:10, x:0, y:0

参考