将所有基类声明为抽象类，并让子类继承并扩展基类。具体类应该是叶子类，不再扩展其他类。以下是示例代码：

// 抽象基类 public abstract class AbstractShape { public abstract void draw(); }

// 具体叶子类 public class Square extends AbstractShape { @Override public void draw() { // 画正方形的实现代码 } }

public class Circle extends AbstractShape { @Override public void draw() { // 画圆形的实现代码 } }

// 抽象中间类 public abstract class AbstractShapeDecorator extends AbstractShape { protected AbstractShape decoratedShape;

public AbstractShapeDecorator(AbstractShape decoratedShape) {
    this.decoratedShape = decoratedShape;
}

}

// 具体装饰器类 public class RedShapeDecorator extends AbstractShapeDecorator { public RedShapeDecorator(AbstractShape decoratedShape) { super(decoratedShape); }

@Override
public void draw() {
    decoratedShape.draw();
    setRedBorder(decoratedShape);
}

private void setRedBorder(AbstractShape decoratedShape){
    // 设置红色边框的实现代码
}

}