Added in API level 9

Console

class Console : Flushable

kotlin.Any
↳	java.io.Console

Methods to access the character-based console device, if any, associated with the current Java virtual machine.

Whether a virtual machine has a console is dependent upon the underlying platform and also upon the manner in which the virtual machine is invoked. If the virtual machine is started from an interactive command line without redirecting the standard input and output streams then its console will exist and will typically be connected to the keyboard and display from which the virtual machine was launched. If the virtual machine is started automatically, for example by a background job scheduler, then it will typically not have a console.

If this virtual machine has a console then it is represented by a unique instance of this class which can be obtained by invoking the java.lang.System#console() method. If no console device is available then an invocation of that method will return null.

Read and write operations are synchronized to guarantee the atomic completion of critical operations; therefore invoking methods readLine(), readPassword(), format(), printf() as well as the read, format and write operations on the objects returned by reader() and writer() may block in multithreaded scenarios.

Invoking close() on the objects returned by the reader() and the writer() will not close the underlying stream of those objects.

The console-read methods return null when the end of the console input stream is reached, for example by typing control-D on Unix or control-Z on Windows. Subsequent read operations will succeed if additional characters are later entered on the console's input device.

Unless otherwise specified, passing a null argument to any method in this class will cause a NullPointerException to be thrown.

Security note: If an application needs to read a password or other secure data, it should use readPassword() or readPassword(java.lang.String,java.lang.Object...) and manually zero the returned character array after processing to minimize the lifetime of sensitive data in memory.

<code>Console cons;
  char[] passwd;
  if ((cons = System.console()) != null &amp;&amp;
      (passwd = cons.readPassword("[%s]", "Password:")) != null) {
      ...
      java.util.Arrays.fill(passwd, ' ');
  }
  </code>

Summary

Public methods
Charset!	charset() Returns the Charset object used for the Console.
Unit	flush() Flushes the console and forces any buffered output to be written immediately .
Console!	format(fmt: String!, vararg args: Any!) Writes a formatted string to this console's output stream using the specified format string and arguments.
Console!	printf(format: String!, vararg args: Any!) A convenience method to write a formatted string to this console's output stream using the specified format string and arguments.
String!	readLine(fmt: String!, vararg args: Any!) Provides a formatted prompt, then reads a single line of text from the console.
String!	readLine() Reads a single line of text from the console.
CharArray!	readPassword(fmt: String!, vararg args: Any!) Provides a formatted prompt, then reads a password or passphrase from the console with echoing disabled.
CharArray!	readPassword() Reads a password or passphrase from the console with echoing disabled
Reader!	reader() Retrieves the unique Reader object associated with this console.
PrintWriter!	writer() Retrieves the unique PrintWriter object associated with this console.

Public methods

charset

Added in API level 35

fun charset(): Charset!

Returns the Charset object used for the Console.

The returned charset corresponds to the input and output source (e.g., keyboard and/or display) specified by the host environment or user. It may not necessarily be the same as the default charset returned from Charset.defaultCharset().

Return
Charset!	a Charset object used for the Console

flush

Added in API level 9

fun flush(): Unit

Flushes the console and forces any buffered output to be written immediately .

Exceptions
java.io.IOException	If an I/O error occurs

format

Added in API level 9

fun format(
    fmt: String!, 
    vararg args: Any!
): Console!

Writes a formatted string to this console's output stream using the specified format string and arguments.

Parameters
fmt	String!: A format string as described in Format string syntax
args	Any!: Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

Return
Console!	This console

Exceptions
java.util.IllegalFormatException	If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.

printf

Added in API level 9

fun printf(
    format: String!, 
    vararg args: Any!
): Console!

A convenience method to write a formatted string to this console's output stream using the specified format string and arguments.

An invocation of this method of the form con.printf(format, args) behaves in exactly the same way as the invocation of

con.format(format, args)

.

Parameters
format	String!: A format string as described in Format string syntax.
args	Any!: Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

Return
Console!	This console

Exceptions
java.util.IllegalFormatException	If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.

readLine

Added in API level 9

fun readLine(
    fmt: String!, 
    vararg args: Any!
): String!

Provides a formatted prompt, then reads a single line of text from the console.

Parameters
fmt	String!: A format string as described in Format string syntax.
args	Any!: Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification.

Return
String!	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.

Exceptions
java.util.IllegalFormatException	If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
java.io.IOError	If an I/O error occurs.

readLine

Added in API level 9

fun readLine(): String!

Reads a single line of text from the console.

Return
String!	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.

Exceptions
java.io.IOError	If an I/O error occurs.

readPassword

Added in API level 9

fun readPassword(
    fmt: String!, 
    vararg args: Any!
): CharArray!

Provides a formatted prompt, then reads a password or passphrase from the console with echoing disabled.

Parameters
fmt	String!: A format string as described in Format string syntax for the prompt text.
args	Any!: Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java Virtual Machine Specification.

Return
CharArray!	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.

Exceptions
java.util.IllegalFormatException	If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
java.io.IOError	If an I/O error occurs.

readPassword

Added in API level 9

fun readPassword(): CharArray!

Reads a password or passphrase from the console with echoing disabled

Return
CharArray!	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.

Exceptions
java.io.IOError	If an I/O error occurs.

reader

Added in API level 9

fun reader(): Reader!

Retrieves the unique Reader object associated with this console.

This method is intended to be used by sophisticated applications, for example, a java.util.Scanner object which utilizes the rich parsing/scanning functionality provided by the Scanner:

Console con = System.console();
  if (con != null) {
      Scanner sc = new Scanner(con.reader());
      ...
  }
  

For simple applications requiring only line-oriented reading, use #readLine.

The bulk read operations read(char[]) , read(char[], int, int) and read(java.nio.CharBuffer) on the returned object will not read in characters beyond the line bound for each invocation, even if the destination buffer has space for more characters. The Reader's read methods may block if a line bound has not been entered or reached on the console's input device. A line bound is considered to be any one of a line feed ('\n'), a carriage return ('\r'), a carriage return followed immediately by a linefeed, or an end of stream.

Return
Reader!	The reader associated with this console

writer

Added in API level 9

fun writer(): PrintWriter!

Retrieves the unique PrintWriter object associated with this console.

Return
PrintWriter!	The printwriter associated with this console