Use java's Scanner.hasNext() function to determine whether there is another input

Use Java's Scanner.hasNext() function to determine whether there is another input

In Java programming, sometimes we need to read the user's input, but it is often impossible to determine how many values ​​the user will enter. . To solve this problem, Java provides the Scanner class to read the standard input stream.

The Scanner class is an important class in the Java standard library. It provides a variety of methods to read different types of values ​​​​in the standard input stream. Among them, hasNext() is a very practical function of the Scanner class, which can be used to determine whether there is the next readable value in the input stream.

The return value of the hasNext() function is of Boolean type. If there is the next readable value in the input stream, it returns true, otherwise it returns false. This function is usually used in conjunction with other reading functions (such as nextInt(), nextDouble(), etc.) to ensure that before reading the value, it is first determined whether there is a next value in the input stream.

The following is a sample code that demonstrates how to use the hasNext() function to determine whether there is another input in the input stream:

import java.util.Scanner;

public class ScannerDemo {
    public static void main(String[] args) {
        // 创建Scanner对象
        Scanner scanner = new Scanner(System.in);
        
        // 使用hasNext()函数判断输入流中是否还有下一个输入
        while (scanner.hasNext()) {
            // 读取整数值
            int number = scanner.nextInt();
            
            // 输出读取到的整数值
            System.out.println("读取到的整数值为：" + number);
        }
        
        // 关闭Scanner对象
        scanner.close();
    }
}

In the above sample code, we first create Scanner object, its parameter is System.in, which means reading data from the standard input stream. Then, use the hasNext() function in the while loop to determine whether there is another input in the input stream. If there is another input in the input stream, call the nextInt() function to read the value and output the read integer value. In this way, multiple input integer values ​​can be read one by one and output. Finally, when there is no next input in the input stream, exit the loop and close the Scanner object.

To summarize, using Java's Scanner.hasNext() function can easily determine whether there is another input in the input stream. In practical applications, we can use this function in conjunction with other reading functions to ensure that before reading the value, we first determine whether there is a next value in the input stream. This can avoid exception errors caused by no next input and improve the robustness and user experience of the program.

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