import java.util.Scanner;  // Import the Scanner class

class Main { // Main is the class name
  public static void main(String[] args) {
    Scanner myObj = new Scanner(System.in);  // Create a Scanner object
    System.out.println("Enter username");

    String userName = myObj.nextLine();  // Read user input
    System.out.println("Username is: " + userName);  // Output user input
  }
}

import java.util.Scanner;  // Import the Scanner class

class Main { // Main is the class name
  public static void main(String[] args) {
    Scanner myObj = new Scanner(System.in);  // Create a Scanner object
    System.out.println("Enter username");

    String userName = myObj.nextLine();  // Read user input
    System.out.println("Username is: " + userName);  // Output user input
  }
}

Scanner scan = new Scanner(System.in);
String myLine = scan.nextLine();

说明java.util.Scanner如何工作的一个简单示例是从System.in中读取单个整数。这真的很简单。

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

要检索用户名，我可能会使用sc.nextLine()。

System.out.println("Enter your username: ");
Scanner scanner = new Scanner(System.in);
String username = scanner.nextLine();
System.out.println("Your username is " + username);

如果您想对输入进行更多控制，或者只是验证用户名变量，也可以使用next(字符串模式)。

你可以在java.util.Scanner的API文档中找到更多关于它们实现的信息

从控制台读取数据

BufferedReader is synchronized, so read operations on a BufferedReader can be safely done from multiple threads. The buffer size may be specified, or the default size(8192) may be used. The default is large enough for most purposes. readLine() « just reads data line by line from the stream or source. A line is considered to be terminated by any one these: \n, \r (or) \r\n Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace(\s) and it is recognised by Character.isWhitespace. « Until the user enters data, the scanning operation may block, waiting for input. « Use Scanner(BUFFER_SIZE = 1024) if you want to parse a specific type of token from a stream. « A scanner however is not thread safe. It has to be externally synchronized. next() « Finds and returns the next complete token from this scanner. nextInt() « Scans the next token of the input as an int.

Code

String name = null;
int number;

java.io.BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
name = in.readLine(); // If the user has not entered anything, assume the default value.
number = Integer.parseInt(in.readLine()); // It reads only String,and we need to parse it.
System.out.println("Name " + name + "\t number " + number);

java.util.Scanner sc = new Scanner(System.in).useDelimiter("\\s");
name = sc.next();  // It will not leave until the user enters data.
number = sc.nextInt(); // We can read specific data.
System.out.println("Name " + name + "\t number " + number);

// The Console class is not working in the IDE as expected.
java.io.Console cnsl = System.console();
if (cnsl != null) {
    // Read a line from the user input. The cursor blinks after the specified input.
    name = cnsl.readLine("Name: ");
    System.out.println("Name entered: " + name);
}

流的输入和输出

Reader Input:     Output:
Yash 777          Line1 = Yash 777
     7            Line1 = 7

Scanner Input:    Output:
Yash 777          token1 = Yash
                  token2 = 777

有一种从控制台读取的简单方法。

请查看以下代码:

import java.util.Scanner;

    public class ScannerDemo {

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

            // Reading of Integer
            int number = sc.nextInt();

            // Reading of String
            String str = sc.next();
        }
    }

具体理解请参考以下文件。

Doc

现在我们来详细了解一下Scanner类的工作原理:

public Scanner(InputStream source) {
    this(new InputStreamReader(source), WHITESPACE_PATTERN);
}

这是用于创建Scanner实例的构造函数。

这里我们传递的是InputStream引用，它只是一个System.In。在这里，它打开了用于控制台输入的InputStream管道。

public InputStreamReader(InputStream in) {
    super(in);
    try {
        sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## Check lock object
    }
    catch (UnsupportedEncodingException e) {
        // The default encoding should always be available
        throw new Error(e);
    }
}

通过系统。在这段代码中，将打开套接字以从控制台读取。