Practice›Java Fundamentals›Module 8. Interfaces & Abstract Classes›8.4 Choosing

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8.4 Choosing — label everything printable

Total: 0 / 3 pts

Practice mode — check each part and get hints as you go.

Task

Fill in labelAll so that it returns every item's label(), joined by single spaces.

The array holds a Rect (a Shape) and a Tag (not a Shape at all) — they share only the Printable contract, yet one loop handles both. The program prints [Rect] <hi>.

Your solution

interface Printable {
    String label();
}

interface Sized {
    int size();
}

abstract class Shape {
    private String name;

    public Shape(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public abstract double area();
}

class Rect extends Shape implements Printable {
    private double w;
    private double h;

    public Rect(double w, double h) {
        super("Rect");
        this.w = w;
        this.h = h;
    }

    public double area() {
        return w * h;
    }

    public String label() {
        return "[" + getName() + "]";
    }
}

class Tag implements Printable, Sized {
    private String text;

    public Tag(String text) {
        this.text = text;
    }

    public String label() {
        return "<" + text + ">";
    }

    public int size() {
        return text.length();
    }
}

public class Main {

    public static String labelAll(Printable[] items) {
        // join every label() with a single space between them

    }

    public static void main(String[] args) {
        Printable[] items = {new Rect(2, 3), new Tag("hi")};
        System.out.println(labelAll(items));
    }
}

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