如何描述嵌套对象的类型？如何描述联合类型？

// 嵌套对象的类型描述
const person = {
  name: 'John',
  age: 30,
  address: {
    street: '123 Main St',
    city: 'New York',
    country: 'USA'
  }
};

// 访问嵌套对象的属性
console.log(person.name); // 输出：John
console.log(person.address.city); // 输出：New York

// 嵌套对象的类型描述
public class Person {
  private String name;
  private int age;
  private Address address;

  // 构造函数
  public Person(String name, int age, Address address) {
    this.name = name;
    this.age = age;
    this.address = address;
  }

  // Getter和Setter方法
  // ...

  // 内部类描述嵌套的Address对象类型
  public class Address {
    private String street;
    private String city;
    private String country;

    // 构造函数
    public Address(String street, String city, String country) {
      this.street = street;
      this.city = city;
      this.country = country;
    }

    // Getter和Setter方法
    // ...
  }
}

// 创建嵌套对象
Person.Address address = new Person.Address("123 Main St", "New York", "USA");
Person person = new Person("John", 30, address);

// 访问嵌套对象的属性
System.out.println(person.getName()); // 输出：John
System.out.println(person.getAddress().getCity()); // 输出：New York

// 联合类型的描述
let value: string | number;

value = 'Hello'; // 字符串类型
console.log(value.length); // 输出：5

value = 42; // 数字类型
console.log(value.toFixed(2)); // 输出：42.00

// 联合类型的描述
public interface Shape {
  void draw();
}

public class Circle implements Shape {
  @Override
  public void draw() {
    System.out.println("Drawing a circle");
  }
}

public class Rectangle implements Shape {
  @Override
  public void draw() {
    System.out.println("Drawing a rectangle");
  }
}

// 使用联合类型的变量
Shape shape;

shape = new Circle();
shape.draw(); // 输出：Drawing a circle

shape = new Rectangle();
shape.draw(); // 输出：Drawing a rectangle