Is there an easy way to read a single char from the console as the user is typing it in Java? Is it possible? I've tried with these methods but they all wait for the user to press enter key:
char tmp = (char) System.in.read();
char tmp = (char) new InputStreamReader(System.in).read ();
char tmp = (char) System.console().reader().read(); // Java 6
I'm starting to think that System.in is not aware of the user input until enter is pressed.
There is no portable way to read raw characters from a Java console.
Some platform-dependent workarounds have been presented above. But to be really portable, you'd have to abandon console mode and use a windowing mode, e.g. AWT or Swing.
You need to knock your console into raw mode. There is no built-in platform-independent way of getting there. jCurses might be interesting, though.
On a Unix system, this might work:
String[] cmd = {"/bin/sh", "-c", "stty raw </dev/tty"};
Runtime.getRuntime().exec(cmd).waitFor();
I have written a Java class RawConsoleInput that uses JNA to call operating system functions of Windows and Unix/Linux.
_kbhit()
and _getwch()
from msvcrt.dll.tcsetattr()
to switch the console to non-canonical mode, System.in.available()
to check whether data is available and System.in.read()
to read bytes from the console. A CharsetDecoder
is used to convert bytes to characters.It supports non-blocking input and mixing raw mode and normal line mode input.
Use jline3:
Example:
Terminal terminal = TerminalBuilder.builder()
.jna(true)
.system(true)
.build();
// raw mode means we get keypresses rather than line buffered input
terminal.enterRawMode();
reader = terminal .reader();
...
int read = reader.read();
....
reader.close();
terminal.close();
Source: Stackoverflow.com