深入理解Java装饰者模式与内部方法调用：一种设计考量

// 1. 组件接口 (Component Interface)
public interface Flag {
    int wave();
    int calculateWind();
}

// 2. 具体组件 (Concrete Component)
public class FlagImpl implements Flag {
    @Override
    public int wave() {
        System.out.println("FlagImpl: Waving. Internal wind calculation result: " + calculateWind());
        return calculateWind(); // 内部调用 FlagImpl 自身的 calculateWind()
    }

    @Override
    public int calculateWind() {
        System.out.println("FlagImpl: Executing base wind calculation.");
        return 8;
    }
}

// 3. 抽象装饰器 (Abstract Decorator)
// 修正了原始问题中装饰器方法的错误递归调用
public abstract class FlagDecorator implements Flag {
    protected Flag decoratedFlag; // 持有被装饰对象的引用

    public FlagDecorator(Flag decoratedFlag) {
        this.decoratedFlag = decoratedFlag;
    }

    @Override
    public int wave() {
        // 默认行为：委托给被装饰对象
        return decoratedFlag.wave();
    }

    @Override
    public int calculateWind() {
        // 默认行为：委托给被装饰对象
        return decoratedFlag.calculateWind();
    }
}

// 4. 具体装饰器 (Concrete Decorator)
public class EnhancedFlagDecorator extends FlagDecorator {

    public EnhancedFlagDecorator(Flag decoratedFlag) {
        super(decoratedFlag);
    }

    @Override
    public int wave() {
        System.out.println("EnhancedFlagDecorator: Adding pre-wave action.");
        int result = decoratedFlag.wave(); // 委托给被装饰对象的 wave() 方法
        System.out.println("EnhancedFlagDecorator: Adding post-wave action.");
        return result + 10; // 增强行为
    }

    @Override
    public int calculateWind() {
        System.out.println("EnhancedFlagDecorator: Modifying wind calculation.");
        // 委托给被装饰对象的 calculateWind() 并进行修改
        return decoratedFlag.calculateWind() + 5;
    }
}

public class DecoratorDemo {
    public static void main(String[] args) {
        Flag flag = new EnhancedFlagDecorator(new FlagImpl());
        System.out.println("Result of wave(): " + flag.wave());
        System.out.println("---");
        System.out.println("Result of calculateWind() directly: " + flag.calculateWind());
    }
}

EnhancedFlagDecorator: Adding pre-wave action.
FlagImpl: Waving. Internal wind calculation result: 8
FlagImpl: Executing base wind calculation.
EnhancedFlagDecorator: Adding post-wave action.
Result of wave(): 18
---
EnhancedFlagDecorator: Modifying wind calculation.
FlagImpl: Executing base wind calculation.
Result of calculateWind() directly: 13

// 1. 抽象基类 (Abstract Base Class)
// 包含可被子类重写的方法
public abstract class AbstractFlag {
    public int calculateWind() {
        System.out.println("AbstractFlag: Executing base wind calculation.");
        return 8;
    }

    public int wave() {
        System.out.println("AbstractFlag: Waving. Wind calculated by current instance: " + calculateWind());
        // 这里的 this.calculateWind() 会根据运行时类型调用子类重写的方法（如果存在）
        return calculateWind();
    }
}

// 2. 具体实现类 (Concrete Implementation)
public class SimpleFlag extends AbstractFlag {
    // 可以不重写任何方法，直接使用父类实现
}

// 3. 扩展类 (Extended Class) - 模拟“装饰”行为，但通过继承实现
public class ExtendedFlag extends AbstractFlag {
    @Override
    public int wave() {
        System.out.println("ExtendedFlag: Adding pre-wave action.");
        int result = super.wave() + 100; // 调用父类的 wave() 方法
        System.out.println("ExtendedFlag: Adding post-wave action.");
        return result;
    }

    @Override
    public int calculateWind() {
        System.out.println("ExtendedFlag: Modifying wind calculation.");
        return super.calculateWind() + 300; // 调用父类的 calculateWind() 方法并增强
    }
}

public class InheritanceDemo {
    public static void main(String[] args) {
        AbstractFlag flag = new ExtendedFlag();
        System.out.println("Result of wave(): " + flag.wave());
        System.out.println("---");
        System.out.println("Result of calculateWind() directly: " + flag.calculateWind());
    }
}

ExtendedFlag: Adding pre-wave action.
AbstractFlag: Waving. Wind calculated by current instance: 308
ExtendedFlag: Modifying wind calculation.
AbstractFlag: Executing base wind calculation.
ExtendedFlag: Adding post-wave action.
Result of wave(): 408
---
ExtendedFlag: Modifying wind calculation.
AbstractFlag: Executing base wind calculation.
Result of calculateWind() directly: 308