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。

举个简单的例子:

import java.util.Scanner;

public class Example
{
    public static void main(String[] args)
    {
        int number1, number2, sum;

        Scanner input = new Scanner(System.in);

        System.out.println("Enter First multiple");
        number1 = input.nextInt();

        System.out.println("Enter second multiple");
        number2 = input.nextInt();

        sum = number1 * number2;

        System.out.printf("The product of both number is %d", sum);
    }
}

你可以流动这段代码:

Scanner obj= new Scanner(System.in);
String s = obj.nextLine();

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

input.nextInt()方法有问题——它只读取int值。

因此，当使用input.nextLine()读取下一行时，您会收到“\n”，即回车键。所以要跳过这个，你必须添加input.nextLine()。

试着这样做:

 System.out.print("Insert a number: ");
 int number = input.nextInt();
 input.nextLine(); // This line you have to add (it consumes the \n character)
 System.out.print("Text1: ");
 String text1 = input.nextLine();
 System.out.print("Text2: ");
 String text2 = input.nextLine();

当用户输入他/她的用户名时，也检查是否有有效的输入。

java.util.Scanner input = new java.util.Scanner(System.in);
String userName;
final int validLength = 6; // This is the valid length of an user name

System.out.print("Please enter the username: ");
userName = input.nextLine();

while(userName.length() < validLength) {

    // If the user enters less than validLength characters
    // ask for entering again
    System.out.println(
        "\nUsername needs to be " + validLength + " character long");

    System.out.print("\nPlease enter the username again: ");
    userName = input.nextLine();
}

System.out.println("Username is: " + userName);