设计模式-行为型模式-策略模式

策略模式（Strategy）：它定义了算法家族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化，不会影响到使用算法的客户。[DP]

//首先，我们定义一个策略接口：


public interface Strategy {
    public int doOperation(int num1, int num2);
}
//接着，我们创建实现了策略接口的具体策略类：


public class OperationAdd implements Strategy {
    @Override
    public int doOperation(int num1, int num2) {
        return num1 + num2;
    }
}

public class OperationSubtract implements Strategy {
    @Override
    public int doOperation(int num1, int num2) {
        return num1 - num2;
    }
}

public class OperationMultiply implements Strategy {
    @Override
    public int doOperation(int num1, int num2) {
        return num1 * num2;
    }
}
//然后，我们创建一个上下文类，它接受一个策略对象并使用该策略对象执行操作：


public class Context {
    private Strategy strategy;

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

    public int executeStrategy(int num1, int num2) {
        return strategy.doOperation(num1, num2);
    }
}
//最后，我们编写客户端代码来演示如何使用策略模式：


public class StrategyPatternDemo {
    public static void main(String[] args) {
        Context context = new Context(new OperationAdd());    
        System.out.println("10 + 5 = " + context.executeStrategy(10, 5));

        context = new Context(new OperationSubtract());    
        System.out.println("10 - 5 = " + context.executeStrategy(10, 5));

        context = new Context(new OperationMultiply());    
        System.out.println("10 * 5 = " + context.executeStrategy(10, 5));
    }
}