Java 中的 Java.io.Console 类

原文:https://www.geeksforgeeks.org/java-io-console-class-java/

Java.io.Console 类提供了访问与当前 Java 虚拟机关联的基于字符的控制台设备(如果有)的方法。控制台类是由 JDK 6 添加到 java.io 中的。

要点:

• 它用于从控制台读写(如果有)。
• 控制台主要是一个便利类，因为它的大部分功能都可以通过 System.in 和 System.out 获得。但是，它的使用可以简化某些类型的控制台交互，尤其是在从控制台读取字符串时。

• Console supplies no constructors. Instead, a Console object is obtained by calling System.console( ), which is shown here:

  java static Console console( )

  如果控制台可用，则返回对它的引用。否则，返回 null。控制台并非在所有情况下都可用。因此，如果返回空值，就不可能有控制台输入/输出。

• 它提供了读取文本和密码的方法。如果您使用控制台类读取密码，它将不会显示给用户。java.io.Console 类与系统控制台内部相连。

重要方法:

• writer : 检索与此控制台关联的唯一 PrintWriter 对象。 语法:

public PrintWriter writer() 
Returns: The printwriter associated with this console

• 读取器:检索与此控制台关联的唯一读取器对象。 语法:

  ```java public Reader reader()
  Returns: The reader associated with this console

  ```

  • 格式:使用指定的格式字符串和参数将格式化字符串写入控制台的输出流。 语法:

  ```java public Console format(String fmt, Object... args) Parameters: fmt - A format string as described in Format string syntax args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. Returns:This console Throws: IllegalFormatException

  ```

  • printf : 使用指定的格式字符串和参数将格式化字符串写入控制台输出流的便捷方法。 语法:

  ```java public Console printf(String format, Object... args) Parameters: format - A format string as described in Format string syntax. args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. Returns:This console Throws:IllegalFormatException

  ```

  • readLine : 提供格式化提示，然后从控制台读取单行文本。 语法:

  ```java public String readLine(String fmt,Object... args) Parameters: fmt - A format string as described in Format string syntax. args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. Returns: A string containing the line read from the console, not including any line-termination characters, or null if an end of stream has been reached. Throws: IllegalFormatException IOError - If an I/O error occurs.

  ```

  • 读取线:从控制台读取单行文本。 语法:

  ```java public String readLine() Returns: A string containing the line read from the console, not including any line-termination characters, or null if an end of stream has been reached. Throws: IOError

  ```

  • 读取密码:提供格式化提示，然后在禁用回显的情况下从控制台读取密码或密码短语。 语法:

  java public char[] readPassword(String fmt,Object... args) Parameters: fmt - A format string as described in Format string syntax for the prompt text. args - Arguments referenced by the format specifiers in the format string. Returns: A character array containing the password or passphrase read from the console, not including any line-termination characters, or null if an end of stream has been reached. Throws: IllegalFormatException IOError

  • 读取密码:从禁用回显的控制台读取密码或密码短语 语法:

  java public char[] readPassword() Returns: A character array containing the password or passphrase read from the console, not including any line-termination characters, or null if an end of stream has been reached. Throws:IOError

  • flush : Flushes the console and forces any buffered output to be written immediately . Syntax:

  java public void flush() Specified by: flush in interface Flushable

  程序:

  ```java // Java Program to demonstrate Console Methods

  import java.io.*; class ConsoleDemo  {     public static void main(String args[])      {         String str;

  //Obtaining a reference to the console.         Console con = System.console();

  // Checking If there is no console available, then exit.         if(con == null)          {             System.out.print("No console available");             return;         }

  // Read a string and then display it.         str = con.readLine("Enter your name: ");         con.printf("Here is your name: %s\n", str);

  //to read password and then display it         System.out.println("Enter the password: ");         char[] ch=con.readPassword();

  //converting char array into string         String pass = String.valueOf(ch);         System.out.println("Password is: " + pass);     } } ```

  输出:

  ```java Enter your name: Nishant Sharma Here is your name: Nishant Sharma Enter the password: Password is: dada

  ```

  注意:System.console()在联机 IDE 中返回空值

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