Top Description Fields Constructors Methods
java.io

public sealed Class Console

extends Object
implements Flushable
permits ProxyingConsole
Class Inheritance
All Implemented Interfaces
java.io.Flushable
Known Direct Subclasses
java.io.ProxyingConsole
Imports
java.security.AccessController, .PrivilegedAction, java.util.*, java.nio.charset.Charset, jdk.internal.access.JavaIOAccess, .SharedSecrets, jdk.internal.io.JdkConsoleImpl, .JdkConsoleProvider, jdk.internal.javac.PreviewFeature, jdk.internal.util.StaticProperty, sun.security.action.GetPropertyAction
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 may 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.

Operations that format strings are locale sensitive, using either the specified Locale, or the default format Locale to produce localized formatted strings.

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(String, Object...) and manually zero the returned character array after processing to minimize the lifetime of sensitive data in memory.

Console cons; char[] passwd; if ((cons = System.console()) != null && (passwd = cons.readPassword("[%s]", "Password:")) != null) { ... java.util.Arrays.fill(passwd, ' '); } 
Console cons;
char[] passwd;
if ((cons = System.console()) != null &&
    (passwd = cons.readPassword("[%s]", "Password:")) != null) {
    ...
    java.util.Arrays.fill(passwd, ' ');
}
Author
Xueming Shen
Since
1.6

Field Summary

Modifier and TypeField and Description
pack-priv static final Charset
CHARSET

private static final Console
cons

private static final boolean
istty

Constructor Summary

AccessConstructor and Description
pack-priv
Console()

Package private no-arg constructor.

Method Summary

Modifier and TypeMethod and Description
public Charset

Returns:

a Charset object used for the Console
charset()

Returns the Charset object used for the Console.

private static native String
encoding()

public void
flush()

Implements java.io.Flushable.flush.

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

public Console

Returns:

This console
format(String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public Console

Returns:

This console
format(Locale
The locale to apply during formatting. If locale is null then no localization is applied.
locale, String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

private static Console
instantiateConsole()

public boolean

Returns:

true if the Console instance is a terminal
isTerminal()

Returns true if the Console instance is a terminal.

private static native boolean
istty()

private static UnsupportedOperationException
newUnsupportedOperationException()

public Console

Returns:

This console
printf(String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public Console

Returns:

This console
printf(Locale
The locale to apply during formatting. If locale is null then no localization is applied.
locale, String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public Console

Returns:

This console
println(Object
An object whose string representation is to be written, may be null.
obj)
Preview Third Preview of Implicitly Declared Classes and Instance Main Methods (JEP 477).

Writes a string representation of the specified object to this console's output stream, terminates the line using System#lineSeparator() and then flushes the console.

public Reader

Returns:

The reader associated with this console
reader()

Retrieves the unique Reader object associated with this console.

public String

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.
readLine(String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

Provides a formatted prompt using the default format locale, then reads a single line of text from the console.

public String

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.
readLine(Locale
The locale to apply during formatting. If locale is null then no localization is applied.
locale, String
A format string as described in Format string syntax.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public String

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.
readLine()

Reads a single line of text from the console.

public String

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 without having read any characters.
readln(String
A prompt string, may be null.
prompt)
Preview Third Preview of Implicitly Declared Classes and Instance Main Methods (JEP 477).

Writes a prompt as if by calling print, then reads a single line of text from this console.

public char[]

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.
readPassword(String
A format string as described in Format string syntax for the prompt text.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public char[]

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.
readPassword(Locale
The locale to apply during formatting. If locale is null then no localization is applied.
locale, String
A format string as described in Format string syntax for the prompt text.
format, Object...
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 behavior on a null argument depends on the conversion.
args)

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

public char[]

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.
readPassword()

Reads a password or passphrase from the console with echoing disabled.

public PrintWriter

Returns:

The printwriter associated with this console
writer()

Retrieves the unique PrintWriter object associated with this console.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Field Detail

CHARSETback to summary
pack-priv static final Charset CHARSET
consback to summary
private static final Console cons
isttyback to summary
private static final boolean istty

Constructor Detail

Consoleback to summary
pack-priv Console()

Package private no-arg constructor.

Method Detail

charsetback to summary
public 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().

Returns:Charset

a Charset object used for the Console

Since
17
encodingback to summary
private static native String encoding()
flushback to summary
public void flush()

Implements java.io.Flushable.flush.

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

formatback to summary
public Console format(String format, Object... args)

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

Parameters
format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:Console

This console

Exceptions
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.
formatback to summary
public Console format(Locale locale, String format, Object... args)

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

Parameters
locale:Locale

The locale to apply during formatting. If locale is null then no localization is applied.

format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:Console

This console

Exceptions
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.
Since
23
instantiateConsoleback to summary
private static Console instantiateConsole()
Annotations
@SuppressWarnings:removal
isTerminalback to summary
public boolean isTerminal()

Returns true if the Console instance is a terminal.

This method returns true if the console device, associated with the current Java virtual machine, is a terminal, typically an interactive command line connected to a keyboard and display.

Implementation Note

The default implementation returns the value equivalent to calling isatty(stdin/stdout) on POSIX platforms, or whether standard in/out file descriptors are character devices or not on Windows.

Returns:boolean

true if the Console instance is a terminal

Since
22
isttyback to summary
private static native boolean istty()
newUnsupportedOperationExceptionback to summary
private static UnsupportedOperationException newUnsupportedOperationException()
printback to summary
public Console print(Object obj)

Preview

Third Preview of Implicitly Declared Classes and Instance Main Methods (JEP 477).

Programs can only use print when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.

Writes a string representation of the specified object to this console's output stream and then flushes the console.

The string representation of the specified object is obtained as if by calling String#valueOf(Object).

Parameters
obj:Object

An object whose string representation is to be written, may be null.

Returns:Console

This console

Annotations
@PreviewFeature
feature:IMPLICIT_CLASSES
Since
23
printfback to summary
public Console printf(String format, Object... args)

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

Implementation Specification

This is the same as calling format(format, args).

Parameters
format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:Console

This console

Exceptions
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.
printfback to summary
public Console printf(Locale locale, String format, Object... args)

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

Implementation Specification

This is the same as calling format(locale, format, args).

Parameters
locale:Locale

The locale to apply during formatting. If locale is null then no localization is applied.

format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:Console

This console

Exceptions
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.
Since
23
printlnback to summary
public Console println(Object obj)

Preview

Third Preview of Implicitly Declared Classes and Instance Main Methods (JEP 477).

Programs can only use println when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.

Writes a string representation of the specified object to this console's output stream, terminates the line using System#lineSeparator() and then flushes the console.

The string representation of the specified object is obtained as if by calling String#valueOf(Object).

Parameters
obj:Object

An object whose string representation is to be written, may be null.

Returns:Console

This console

Annotations
@PreviewFeature
feature:IMPLICIT_CLASSES
Since
23
readerback to summary
public 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()); code: } 
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.

Returns:Reader

The reader associated with this console

readLineback to summary
public String readLine(String format, Object... args)

Provides a formatted prompt using the default format locale, then reads a single line of text from the console.

Parameters
format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns: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
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.
IOError:
If an I/O error occurs.
readLineback to summary
public String readLine(Locale locale, String format, Object... args)

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

Parameters
locale:Locale

The locale to apply during formatting. If locale is null then no localization is applied.

format:String

A format string as described in Format string syntax.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns: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
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.
IOError:
If an I/O error occurs.
Since
23
readLineback to summary
public String readLine()

Reads a single line of text from the console.

Returns: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
IOError:
If an I/O error occurs.
readlnback to summary
public String readln(String prompt)

Preview

Third Preview of Implicitly Declared Classes and Instance Main Methods (JEP 477).

Programs can only use readln when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.

Writes a prompt as if by calling print, then reads a single line of text from this console.

Parameters
prompt:String

A prompt string, may be null.

Returns: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 without having read any characters.

Annotations
@PreviewFeature
feature:IMPLICIT_CLASSES
Exceptions
IOError:
If an I/O error occurs.
Since
23
readPasswordback to summary
public char[] readPassword(String format, Object... args)

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

Parameters
format:String

A format string as described in Format string syntax for the prompt text.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:char[]

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
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.
IOError:
If an I/O error occurs.
readPasswordback to summary
public char[] readPassword(Locale locale, String format, Object... args)

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

Parameters
locale:Locale

The locale to apply during formatting. If locale is null then no localization is applied.

format:String

A format string as described in Format string syntax for the prompt text.

args:Object[]

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 behavior on a null argument depends on the conversion.

Returns:char[]

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
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.
IOError:
If an I/O error occurs.
Since
23
readPasswordback to summary
public char[] readPassword()

Reads a password or passphrase from the console with echoing disabled.

Returns:char[]

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
IOError:
If an I/O error occurs.
writerback to summary
public PrintWriter writer()

Retrieves the unique PrintWriter object associated with this console.

Returns:PrintWriter

The printwriter associated with this console