How to read input numbers and letters in java

How to read input numbers and letters in Java? Use the Scanner class to read numbers (nextInt()) and strings (nextLine()). Use the BufferedReader class to read a line of text and parse the number (parseInt()). Use the Console class to read numbers (nextInt()) and strings (readLine()).

How to read entered numbers and letters in Java

There are various methods in Java to control The platform reads the numbers and letters entered by the user:

1. Scanner class

The Scanner class provides nextInt() and nextLine() methods for reading respectively. Numbers and strings.

import java.util.Scanner;

public class ReadInput {

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

        // 读取数字
        int number = scanner.nextInt();

        // 读取字符串（包括空格）
        String inputString = scanner.nextLine();
    }
}

2. BufferedReader class

The BufferedReader class provides the readLine() method for reading a line of text.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ReadInput {

    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        // 读取数字
        int number = Integer.parseInt(reader.readLine());

        // 读取字符串（不包括换行符）
        String inputString = reader.readLine();
    }
}

3. Console class

The Console class (introduced in Java 11) provides a more concise way to read input.

import java.io.Console;

public class ReadInput {

    public static void main(String[] args) {
        Console console = System.console();

        // 读取数字
        int number = console.reader().nextInt();

        // 读取字符串（包括空格）
        String inputString = console.reader().readLine();
    }
}

Note:

• All methods block until the user enters data and presses Enter.
• For numeric input, make sure to check that the number is in the correct format, for example using the Integer.parseInt() or Integer.valueOf() methods.

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