How to check if there is next line in user input using hasNextLine() method of Scanner class

How to use the hasNextLine() method of the Scanner class to check whether there is a next line in the user input

The Scanner class is a commonly used tool class in Java for reading user input. It provides many convenient methods to help us process input. One very useful method is hasNextLine(), which can be used to check whether there is a next line in the user input. This article will introduce how to use the hasNextLine() method of the Scanner class and its related code examples.

First, to use the Scanner class, we need to create a Scanner object first. You can create a Scanner object through the following code:

Scanner scanner = new Scanner(System.in);

The above code will create a Scanner object that will read user input from the standard input (that is, the keyboard). Next, we can use the hasNextLine() method to check if there is a next line in the user input. The hasNextLine() method returns a boolean value, which returns true if there is a next line in the user input; otherwise it returns false.

The following is a sample code that demonstrates how to use the hasNextLine() method to check whether there is a next line in the user input:

import java.util.Scanner;

public class ScannerExample {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入多行文本，以空行结束：");
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();
            if (line.isEmpty()) {
                break;
            }
            System.out.println("您输入的文本是：" + line);
        }
        
        scanner.close();
    }
}

In the above code, we first output a prompt message, Requires the user to enter multiple lines of text, ending with a blank line. Then read the user's input through a while loop until the user input behavior is empty. On each iteration of the loop, we use the hasNextLine() method to check if there is a next line in the user input. If there is a next line, we use the nextLine() method to read the next line of text entered by the user and print it out. If the user input line is a blank line, we use the break statement to break out of the loop and end the reading process.

It should be noted that after using the Scanner class to read user input, the close() method of the Scanner class should be called to release resources.

To summarize, by using the hasNextLine() method of the Scanner class, we can easily check whether there is a next line in the user input. This is useful for handling multi-line text input. I hope the introduction in this article can help you better use the Scanner class to process user input.

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