1. 编写程序实现以下逻辑。 ① 抽象类Animal具有一个抽象方法walk。 ② 接口Flyable具有一个方法fly。 ③ 类Bird继承Animal并实现Flyable。 编写测试类BirdTest，在main方法中构造一个Bird对象并调用其walk和fly方法(重写这2个方法时，打印一行用于模拟的字符串即可)。 2. 接口MobilePhone定义了以下方法： void on(); // 开机 void off(); // 关机 void charge(); // 充电 分别采用如下两种方式创建两个实现MobilePhone接口的类的对象，并在测试类中分别对这两个对象调用上述方法。 ① 编写类IPhone实现MobilePhone接口。 ② 使用实现了MobilePhone接口的匿名内部类。 ③ 使用实现了MobilePhone接口的Lambda表达式。 3. 编写程序模拟用以表示直线的Line类，具体包含以下逻辑： ① 表示直线起点和终点的嵌套类Point，其包含描述横纵坐标的x、y字段。 ② 表示直线方向的嵌套枚举Direction，其包含描述若干方向的枚举常量。 在Line类中编写必要的代码，然后在测试类LineTest中构造几个Line对象并输出每个对象的有关信息。用Java代码写出上边的1、2、3

1.

abstract class Animal {
    public abstract void walk();
}

interface Flyable {
    public void fly();
}

class Bird extends Animal implements Flyable {
    @Override
    public void walk() {
        System.out.println("Bird is walking.");
    }

    @Override
    public void fly() {
        System.out.println("Bird is flying.");
    }
}

public class BirdTest {
    public static void main(String[] args) {
        Bird bird = new Bird();
        bird.walk();
        bird.fly();
    }
}

2.

interface MobilePhone {
    public void on();
    public void off();
    public void charge();
}

class IPhone implements MobilePhone {
    @Override
    public void on() {
        System.out.println("IPhone is turned on.");
    }

    @Override
    public void off() {
        System.out.println("IPhone is turned off.");
    }

    @Override
    public void charge() {
        System.out.println("IPhone is charging.");
    }
}

public class MobilePhoneTest {
    public static void main(String[] args) {
        MobilePhone phone1 = new IPhone();
        phone1.on();
        phone1.charge();
        phone1.off();

        MobilePhone phone2 = new MobilePhone() {
            @Override
            public void on() {
                System.out.println("Anonymous phone is turned on.");
            }

            @Override
            public void off() {
                System.out.println("Anonymous phone is turned off.");
            }

            @Override
            public void charge() {
                System.out.println("Anonymous phone is charging.");
            }
        };
        phone2.on();
        phone2.charge();
        phone2.off();

        MobilePhone phone3 = () -> {
            System.out.println("Lambda phone is turned on.");
            System.out.println("Lambda phone is charging.");
            System.out.println("Lambda phone is turned off.");
        };
        phone3.on();
        phone3.charge();
        phone3.off();
    }
}

3.

class Line {
    static class Point {
        int x;
        int y;

        public Point(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }

    enum Direction {
        HORIZONTAL,
        VERTICAL,
        DIAGONAL
    }

    Point start;
    Point end;
    Direction direction;

    public Line(Point start, Point end) {
        this.start = start;
        this.end = end;
        if (start.x == end.x) {
            direction = Direction.VERTICAL;
        } else if (start.y == end.y) {
            direction = Direction.HORIZONTAL;
        } else {
            direction = Direction.DIAGONAL;
        }
    }

    @Override
    public String toString() {
        return "Line{" +
                "start=" + start.x + "," + start.y +
                ", end=" + end.x + "," + end.y +
                ", direction=" + direction +
                '}';
    }
}

public class LineTest {
    public static void main(String[] args) {
        Line line1 = new Line(new Line.Point(0, 0), new Line.Point(0, 10));
        Line line2 = new Line(new Line.Point(0, 0), new Line.Point(10, 0));
        Line line3 = new Line(new Line.Point(0, 0), new Line.Point(10, 10));
        System.out.println(line1);
        System.out.println(line2);
        System.out.println(line3);
    }
}