Java Reference
In-Depth Information
Solution
Use the Java 6
System.console()
method to obtain a
Console
object, and use its methods.
Discussion
The
Console
class is intended for reading directly from a program's controlling terminal.
When you run an application from a “terminal window” or “command prompt window” on
most systems, its console and its standard input are both connected to the terminal, by de-
fault. However, the standard input can be changed by piping or redirection on most OSes. If
you really want to read from “wherever the user is sitting,” bypassing any indirections, then
the
Console
class is usually your friend.
You cannot instantiate
Console
yourself; you must get an instance from the
System
class's
console()
method. You can then call methods such as
readLine()
, which behaves largely
like the method of the same name in the
BufferedReader
class used in the previous recipe.
The following code shows an example of prompting for a name and reading it from the con-
sole:
src/main/java/io/ConsoleRead.java
public
public class
class
ConsoleRead
ConsoleRead
{
public
public static
void
main
(
String
[]
args
) {
String name
=
System
.
console
().
readLine
(
"What is your name?"
);
System
.
out
.
println
(
"Hello, "
+
name
.
toUpperCase
());
static
void
}
}
One complication is that the
System.console()
method can return
null
if the console isn't
connected. Annoyingly, some IDEs including Eclipse don't manage to set up a controlling
terminal when you use the Run As→Java Application mechanism. So production-quality
code should always check for
null
before trying to use the
Console
. If you do get
null
, you
can fall back to using the code in
Reading Standard Input
.
One facility the
Console
class is quite useful for is reading a password without having it
echo. This has been a standard facility of command-line applications for decades, as the most
obvious way of preventing “shoulder surfing”—looking over your shoulder to see your pass-
word. Nonecho password reading is now supported in Java: the
Console
class has a
readPassword()
method that takes a
prompt
argument, intended to be used like:
