1.创建一个图书类(Book), 并在该类中定义3个成员变量图书编号(id)、 图书名称 (name)以及作者(author), 再定义-一个方法(setBook) 为这3个成员赋值。在main()方法中，词用setBook方法，并将图书编号和图书名称输出。 2使用单例模式实现仅能创建Book类的3个实例。 3.使用方法的重载方式实现计算矩形面积和圆面积的方法。

1. 代码如下：

public class Book {
    private int id;
    private String name;
    private String author;

    public void setBook(int id, String name, String author) {
        this.id = id;
        this.name = name;
        this.author = author;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    public static void main(String[] args) {
        Book book = new Book();
        book.setBook(123, "Java基础教程", "张三");
        System.out.println("图书编号：" + book.getId() + "，图书名称：" + book.getName());
    }
}

2. 单例模式实现代码如下：

public class Book {
    private int id;
    private String name;
    private String author;

    private static Book instance1 = new Book();
    private static Book instance2 = new Book();
    private static Book instance3 = new Book();

    private Book() {}

    public static Book getInstance(int index) {
        switch (index) {
            case 1:
                return instance1;
            case 2:
                return instance2;
            case 3:
                return instance3;
            default:
                return null;
        }
    }

    public void setBook(int id, String name, String author) {
        this.id = id;
        this.name = name;
        this.author = author;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    public static void main(String[] args) {
        Book book1 = Book.getInstance(1);
        book1.setBook(123, "Java基础教程", "张三");
        System.out.println("图书编号：" + book1.getId() + "，图书名称：" + book1.getName());

        Book book2 = Book.getInstance(2);
        book2.setBook(456, "Python基础教程", "李四");
        System.out.println("图书编号：" + book2.getId() + "，图书名称：" + book2.getName());

        Book book3 = Book.getInstance(3);
        book3.setBook(789, "C#基础教程", "王五");
        System.out.println("图书编号：" + book3.getId() + "，图书名称：" + book3.getName());
    }
}

3. 计算矩形面积和圆面积的方法重载代码如下：

public class CalculateArea {
    public static double getArea(double width, double height) {
        return width * height;
    }

    public static double getArea(double radius) {
        return Math.PI * radius * radius;
    }

    public static void main(String[] args) {
        double width = 3.5;
        double height = 5.2;
        double radius = 2.0;

        double rectangleArea = getArea(width, height);
        System.out.println("矩形面积：" + rectangleArea);

        double circleArea = getArea(radius);
        System.out.println("圆面积：" + circleArea);
    }
}