设计一个 Shape 抽象类，包括：~ 成島変量包括顔色 color 和是否填充 filled (boolean)，默込 値力 false i 対 color 和 filled 迸行初始化的枸造方法；← 计算面积 getArea0的抽象方法; 计算周长 getLength的抽象方法；く 设计一个接口 Colorable，包括一个void howToColor(String color)的方法。← 设计一个类 Square，继承 Shape 类，实现 Colorable 接口，。 并包含成変量 length; ← toString(方法，輸出 Square 的面和周K。创建一个测试类，创建一个 Square 对象并输出。

下面是 Shape 抽象类、Colorable 接口、Square 类和测试类的实现：

// Shape 抽象类
abstract class Shape {
    protected String color;
    protected boolean filled;

    public Shape(String color, boolean filled) {
        this.color = color;
        this.filled = filled;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public boolean isFilled() {
        return filled;
    }

    public void setFilled(boolean filled) {
        this.filled = filled;
    }

    public abstract double getArea();

    public abstract double getLength();
}

// Colorable 接口
interface Colorable {
    void howToColor(String color);
}

// Square 类
class Square extends Shape implements Colorable {
    private double length;

    public Square(double length, String color, boolean filled) {
        super(color, filled);
        this.length = length;
    }

    public double getLength() {
        return length;
    }

    public void setLength(double length) {
        this.length = length;
    }

    public double getArea() {
        return length * length;
    }

    public void howToColor(String color) {
        setColor(color);
        System.out.println("Color the square with " + color);
    }

    public String toString() {
        return "Square[length=" + length + ",color=" + color + ",filled=" + filled + "]";
    }
}

// 测试类
public class TestShape {
    public static void main(String[] args) {
        Square square = new Square(5, "red", true);
        System.out.println(square);
        System.out.println("Area: " + square.getArea());
        System.out.println("Perimeter: " + square.getLength());
        square.howToColor("blue");
        System.out.println(square);
    }
}

输出结果如下：

Square[length=5.0,color=red,filled=true]
Area: 25.0
Perimeter: 5.0
Color the square with blue
Square[length=5.0,color=blue,filled=true]