如何使用Java中的Scanner类从控制台读取输入?
如何使用如何使用Java中的Scanner类从控制台读取输入?,java,java.util.scanner,Java,Java.util.scanner,如何使用扫描仪类从控制台读取输入?大概是这样的: System.out.println("Enter your username: "); Scanner = input(); // Or something like this, I don't know the code 基本上,我只想让扫描器读取用户名的输入,并将输入分配给字符串变量。一个简单的例子来说明java.util.scanner的工作原理,就是从系统中读取一个整数。这真的很简单 Scanner scan = new Scanne
扫描仪
类从控制台读取输入?大概是这样的:
System.out.println("Enter your username: ");
Scanner = input(); // Or something like this, I don't know the code
基本上,我只想让扫描器读取用户名的输入,并将输入分配给
字符串变量。一个简单的例子来说明java.util.scanner
的工作原理,就是从系统中读取一个整数。这真的很简单
Scanner scan = new Scanner(System.in);
String myLine = scan.nextLine();
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();
要检索我可能会使用的用户名
如果希望对输入进行更多控制,或者只验证username
变量,也可以使用
Scanner scan = new Scanner(System.in);
String myLine = scan.nextLine();
当用户输入他/她的用户名时,您将在中找到有关其实现的更多信息,同时检查有效输入
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);
java.util.Scanner输入=新的java.util.Scanner(System.in);
字符串用户名;
最终整数有效长度=6;//这是用户名的有效长度
System.out.print(“请输入用户名:”);
userName=input.nextLine();
while(userName.length()
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);
}
}
您可以制作一个简单的程序来询问用户的姓名,并打印回复使用的任何输入
或者让用户输入两个数字,你可以加、乘、减或除这些数字,然后打印用户输入的答案,就像计算器一样
因此,您需要Scanner类。您必须导入java.util.Scanner代码>,并且在需要使用的代码中:
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
看看这有什么不同:input.next()代码>,i=input.nextInt()代码>,d=input.nextDouble()代码>
根据字符串,int和double的变化方式与其他字符串相同。不要忘记代码顶部的import语句。下面是执行所需操作的完整类:
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();
}
}
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);
}
}
import java.util.Scanner;
公共类应用程序{
公共静态void main(字符串[]args){
扫描仪输入=新扫描仪(System.in);
最终有效整数=6;
扫描仪1=新扫描仪(System.in);
System.out.println(“输入您的用户名:”);
字符串s=1.nextLine();
如果(s.length()<有效){
System.out.println(“输入有效用户名”);
System.out.println(
“用户名必须包含“+有效+”字符”);
System.out.println(“再次输入:”;
s=1.nextLine();
}
System.out.println(“接受的用户名:+s”);
扫描器2=新扫描器(System.in);
System.out.println(“输入您的年龄:”;
int a=two.nextInt();
System.out.println(“接受的年龄:+a”);
扫描仪三=新扫描仪(System.in);
System.out.println(“输入您的性别:”;
字符串sex=3.nextLine();
System.out.println(“接受性别:+Sex”);
}
}
要读取输入:
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
要在调用带有某些参数/参数的方法时读取输入,请执行以下操作:
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());
}
if(args.length!=2){
System.err.println(“Utilizare:javagrep”);
系统出口(1);
}
试一试{
grep(args[0],args[1]);
}捕获(IOE异常){
System.out.println(e.getMessage());
}
从控制台读取数据
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);
}
- 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()。对于大多数情况,默认值足够大
«只需从流或源中逐行读取数据。一行被认为是由下列任一行终止:\n\r(或)\r\n
- 使用定界符模式将其输入拆分为标记,默认情况下,定界符模式与空白(\s)匹配,并由识别
«在用户输入数据之前,扫描操作可能会阻塞,等待输入。
«如果要分析流中特定类型的令牌,请使用Scanner()。
«但是,扫描仪不是线程安全的。它必须在外部同步
next()«查找并返回来自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
代码
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);
}
流的输入和输出
有几种方法可以从用户那里获取输入。在本程序中,我们将采用Scanner类来实现该任务。这个Scanner类属于java.util
,因此程序的第一行是import java.util.Scanner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,我们继续编写代码
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,请将新的Scanner对象创建为“in”。现在我们使用它的一种方法,即“下一步”。“next”方法获取用户在键盘上输入的文本字符串
这里我在.nextLine()中使用
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);
}
}
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
请查找以下代码:
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();
}
}
有关详细了解,请参阅以下文件
现在,让我们详细了解Scanner类的工作原理:
public Scanner(InputStream source) {
this(new InputStreamReader(source), WHITESPACE_PATTERN);
}
这是用于创建扫描程序实例的构造函数
这里我们传递的是InputStream
引用,它只不过是一个系统。在这里,它打开控制台输入的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
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);
}
}
Scanner obj= new Scanner(System.in);
String s = obj.nextLine();
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();