如何使用Scanner
该类从控制台读取输入?像这样:
System.out.println("Enter your username: ");
Scanner = input(); // Or something like this, I don't know the code
基本上,我只需要让扫描程序读取用户名的输入,然后将输入分配给String
变量。
如何使用Scanner
该类从控制台读取输入?像这样:
System.out.println("Enter your username: ");
Scanner = input(); // Or something like this, I don't know the code
基本上,我只需要让扫描程序读取用户名的输入,然后将输入分配给String
变量。
Answers:
一个简单的示例来说明如何java.util.Scanner
从中读取单个整数System.in
。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);
next(String pattern)
如果您想对输入进行更多控制,或者仅验证username
变量,也可以使用。
您可以在API文档中找到有关其实现的更多信息java.util.Scanner
从控制台读取数据
BufferedReader
由于是同步的,因此可以从多个线程安全地完成BufferedReader上的读取操作。可以指定缓冲区大小,也可以使用默认大小(8192)。对于大多数用途,默认值足够大。
readLine() « 只是从流或源中逐行读取数据。一条线被以下任何一个终止:\ n,\ r(或)\ r \ n
Scanner
使用定界符模式将其输入分解为标记,默认情况下,该定界符与空格匹配,并由识别Character.isWhitespace
。
« 在用户输入数据之前,扫描操作可能会阻塞,等待输入。 « 如果要从流中解析特定类型的令牌,请使用Scanner(BUFFER_SIZE = 1024)。 « 但是,扫描仪不是线程安全的。它必须在外部同步。
next()«查找并返回此扫描仪的下一个完整令牌。nextInt()«将输入的下一个标记扫描为int。
码
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);
}
Reader Input: Output:
Yash 777 Line1 = Yash 777
7 Line1 = 7
Scanner Input: Output:
Yash 777 token1 = Yash
token2 = 777
BufferedReader, Scanner
从本地文件(OR)网络文件读取数据。
input.nextInt()方法存在问题-它仅读取int值。
因此,当使用input.nextLine()读取下一行时,您会收到“ \ n”,即Enter键。因此,要跳过此步骤,您必须添加input.nextLine()。
像这样尝试:
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();
有几种方法可以从用户那里获取输入。在此程序中,我们将使用Scanner类来完成任务。该Scanner类属于java.util
,因此程序的第一行是import java.util.Scanner;。它允许用户读取Java中各种类型的值。import语句行必须位于Java程序的第一行,我们将继续进行代码编写。
in.nextInt(); // It just reads the numbers
in.nextLine(); // It get the String which user enters
要访问Scanner类中的方法,请创建一个新的扫描仪对象为“ in”。现在,我们使用其方法之一,即“ next”。“下一个”方法获取用户在键盘上输入的文本字符串。
在这里,我in.nextLine();
用来获取用户输入的字符串。
import java.util.Scanner;
class GetInputFromUser {
public static void main(String args[]) {
int a;
float b;
String s;
Scanner in = new Scanner(System.in);
System.out.println("Enter a string");
s = in.nextLine();
System.out.println("You entered string " + s);
System.out.println("Enter an integer");
a = in.nextInt();
System.out.println("You entered integer " + a);
System.out.println("Enter a float");
b = in.nextFloat();
System.out.println("You entered float " + b);
}
}
import java.util.Scanner;
public class ScannerDemo {
public static void main(String[] arguments){
Scanner input = new Scanner(System.in);
String username;
double age;
String gender;
String marital_status;
int telephone_number;
// Allows a person to enter his/her name
Scanner one = new Scanner(System.in);
System.out.println("Enter Name:" );
username = one.next();
System.out.println("Name accepted " + username);
// Allows a person to enter his/her age
Scanner two = new Scanner(System.in);
System.out.println("Enter Age:" );
age = two.nextDouble();
System.out.println("Age accepted " + age);
// Allows a person to enter his/her gender
Scanner three = new Scanner(System.in);
System.out.println("Enter Gender:" );
gender = three.next();
System.out.println("Gender accepted " + gender);
// Allows a person to enter his/her marital status
Scanner four = new Scanner(System.in);
System.out.println("Enter Marital status:" );
marital_status = four.next();
System.out.println("Marital status accepted " + marital_status);
// Allows a person to enter his/her telephone number
Scanner five = new Scanner(System.in);
System.out.println("Enter Telephone number:" );
telephone_number = five.nextInt();
System.out.println("Telephone number accepted " + telephone_number);
}
}
您可以编写一个简单的程序来询问用户名,并打印任何使用输入的答复。
或要求用户输入两个数字,您可以对这些数字进行加,乘,减或除运算,并像计算器的行为一样打印用户输入的答案。
因此,您需要Scanner类。您必须import java.util.Scanner;
,并且在代码中需要使用:
Scanner input = new Scanner(System.in);
input
是一个变量名。
Scanner input = new Scanner(System.in);
System.out.println("Please enter your name: ");
s = input.next(); // Getting a String value
System.out.println("Please enter your age: ");
i = input.nextInt(); // Getting an integer
System.out.println("Please enter your salary: ");
d = input.nextDouble(); // Getting a double
看到这种不同:input.next();
,i = input.nextInt();
,d = input.nextDouble();
根据String的说法,int和double会以相同的方式改变其余部分。不要忘记代码顶部的import语句。
一个简单的例子:
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);
}
}
当用户输入他/她时username
,还要检查输入是否有效。
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);
读取输入:
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
在调用带有某些参数/参数的方法时读取输入:
if (args.length != 2) {
System.err.println("Utilizare: java Grep <fisier> <cuvant>");
System.exit(1);
}
try {
grep(args[0], args[1]);
} catch (IOException e) {
System.out.println(e.getMessage());
}
import java.util.*;
class Ss
{
int id, salary;
String name;
void Ss(int id, int salary, String name)
{
this.id = id;
this.salary = salary;
this.name = name;
}
void display()
{
System.out.println("The id of employee:" + id);
System.out.println("The name of employye:" + name);
System.out.println("The salary of employee:" + salary);
}
}
class employee
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
Ss s = new Ss(sc.nextInt(), sc.nextInt(), sc.nextLine());
s.display();
}
}
这是执行所需操作的完整类:
import java.util.Scanner;
public class App {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
final int valid = 6;
Scanner one = new Scanner(System.in);
System.out.println("Enter your username: ");
String s = one.nextLine();
if (s.length() < valid) {
System.out.println("Enter a valid username");
System.out.println(
"User name must contain " + valid + " characters");
System.out.println("Enter again: ");
s = one.nextLine();
}
System.out.println("Username accepted: " + s);
Scanner two = new Scanner(System.in);
System.out.println("Enter your age: ");
int a = two.nextInt();
System.out.println("Age accepted: " + a);
Scanner three = new Scanner(System.in);
System.out.println("Enter your sex: ");
String sex = three.nextLine();
System.out.println("Sex accepted: " + sex);
}
}
Scanner
。
您可以传递以下代码:
Scanner obj= new Scanner(System.in);
String s = obj.nextLine();
您可以在Java中使用Scanner类
Scanner scan = new Scanner(System.in);
String s = scan.nextLine();
System.out.println("String: " + s);
有一种从控制台读取的简单方法。
请找到以下代码:
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();
}
}
有关详细的理解,请参阅以下文档。
现在,让我们谈谈对Scanner类工作的详细理解:
public Scanner(InputStream source) {
this(new InputStreamReader(source), WHITESPACE_PATTERN);
}
这是用于创建Scanner实例的构造函数。
在这里,我们传递的InputStream
参考只是一个System.In
。在这里,它打开InputStream
管道以供控制台输入。
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);
}
}
通过传递System.in,此代码将打开套接字以从控制台读取。