How to call a class in Java?

To invoke a class, you need to follow these steps:

1. Importing classes: At the beginning of Java code, use the import statement to import the class that needs to be called. For example, to call the Scanner class, you can use import java.util.Scanner;.
2. Creating objects: Use the “new” keyword to create an instance of a class. For example, to create a Scanner object, you can use “Scanner scanner = new Scanner(System.in);”.
3. To call a class method: use the object name followed by a dot to call the class method. For example, to use the nextInt() method of a Scanner object to read an integer, you can use int number = scanner.nextInt();.

Here is a complete example code:

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // 创建Scanner对象
        Scanner scanner = new Scanner(System.in);
        
        // 调用nextInt()方法读取一个整数
        System.out.println("请输入一个整数：");
        int number = scanner.nextInt();
        System.out.println("你输入的整数是：" + number);
        
        // 调用nextLine()方法读取一行字符串
        System.out.println("请输入一行字符串：");
        scanner.nextLine(); // 读取nextInt()方法后的换行符
        String line = scanner.nextLine();
        System.out.println("你输入的字符串是：" + line);
        
        // 关闭Scanner对象
        scanner.close();
    }
}

This sample code utilizes the Scanner class to read integers and strings inputted by the user, and then prints them.