Use java's Scanner.hasNextLong() function to determine whether the next input is a long integer

Use Java's Scanner.hasNextLong() function to determine whether the next input is a long integer

In Java, input and output are common operations and can be implemented through the Scanner class. The Scanner class provides many useful methods to read user input. One of the very useful methods is hasNextLong(), which can determine whether the next input is a long integer. In this article, I will introduce how to use the hasNextLong() function of the Scanner class to determine whether the user's input is a long integer, and provide some sample code.

First, we need to create a Scanner object to read user input from standard input. You can use the following code to create a Scanner object:

Scanner scanner = new Scanner(System.in);

Next, we can use the hasNextLong() function to determine whether the next input is a long integer. The hasNextLong() function returns a Boolean value, which returns true if the next input is a long integer; otherwise, it returns false. We can use if statements in the program to make logical judgments based on the returned results.

The following is a sample code that demonstrates how to use the hasNextLong() function to determine whether the integer entered by the user is a long integer:

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.print("请输入一个整数：");
        if (scanner.hasNextLong()) {
            long num = scanner.nextLong();
            System.out.println("您输入的是长整数：" + num);
        } else {
            String input = scanner.next();
            System.out.println("您输入的是非长整数：" + input);
        }
    }
}

In the above sample code, we first output the prompt message Ask the user to enter an integer. Then, determine whether the next value entered by the user is a long integer by calling the hasNextLong() function. If it is a long integer, we read the value of the long integer by calling the nextLong() function and output the relevant information. If it is not a long integer, read a line of input by calling the next() function and output relevant information.

The following is an example of running the program:

请输入一个整数：123456789
您输入的是长整数：123456789

请输入一个整数：abc123
您输入的是非长整数：abc123

By using the hasNextLong() function of the Scanner class, we can easily determine whether the next value entered by the user is a long integer. This is useful when handling user input to avoid exceptions before typecasting the input. Whether you are doing simple input validation or dealing with specific business needs, Scanner.hasNextLong() is a very useful method.

Summary:
This article introduces how to use the hasNextLong() function of the Scanner class in Java to determine whether the next input is a long integer. By using this function, we can easily determine whether the next value input by the user is a long integer, and perform corresponding processing based on the judgment result. Scanner.hasNextLong() is a very useful method whether in simple input validation or in dealing with specific business needs.

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