JAVA Problem

[denny577]

How can I clear the output screen in JAVA? I made a clock but t just prints the time over and over again

[Dropzone]

It's the \n in the last print call that's preventing it from working properly. There are two ways you could fix it. The first way would be to remove the \n from that last print call, so it just looks like System.out.print(".");. The second way would be to instead change that \n to a \r, at which point you'd no longer need the System.out.print("\r"); call near the start of the program.

[denny577]

The second way would be to instead change that \n to a \r, at which point you'd no longer need the System.out.print("\r"); call near the start of the program.

I did that, but then it prints the time over and over without an empty line in between

[Sacro]

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for (int time = 0; time < 2; time++) {
    		time--;

woud

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for(;;)

not be better?

[denny577]

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for (int time = 0; time < 2; time++) {
    		time--;

woud

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for(;;)

not be better?

When I try that it says that in

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Calendar now = Calendar.getInstance();

now is unreachable code

Otherwise it might help if someone could tell me how to get the backspace command into a variable, then I can let it print that before it prints the again
Something like this:

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    	char bspace = (char) 8;

(Only I don't know what to say for backspace )
then before the clock

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        System.out.print( bspace );

[Dropzone]

Ah, the problem here is Eclipse. It seems that its console view doesn't respond correctly to \r (or \b, which is how you put a backspace in a string). There's probably no way to get this to work in Eclipse's console, although it does work fine if you run the program in a Windows console (cmd.exe).

[Lakie]

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for(;;)

not be better?

In C++ at least, "while (1)" would be much better, the syntax across the languages (C+ and Java) should be pretty much the same too...
Also note that is not "<iteration opener>;" - ( " for(;;); " ), it should surely be " for(;;) { "!

Note that I only know basic C++ so it may or may not work correctly in Java, but most of the examples our teacher gave us for C++ loops were written in Java, oddly enough, apparently because the syntax is the same or extremely close...

~ Lakie

[denny577]

Ah, the problem here is Eclipse. It seems that its console view doesn't respond correctly to \r (or \b, which is how you put a backspace in a string). There's probably no way to get this to work in Eclipse's console, although it does work fine if you run the program in a Windows console (cmd.exe).

Didn't think of that, it does work indeed.

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for(;;)

not be better?

In C++ at least, "while (1)" would be much better

When I try that it says "cannot convert from int to boolean", but my version did work fine anyway

I attached the working version

[Dropzone]

In C++ at least, "while (1)" would be much better

When I try that it says "cannot convert from int to boolean", but my version did work fine anyway

If you wanted to do it that way in Java, you'd have to use while (true) { instead of while (1) { , because Java is more strict about type checking than C++ is. C++ lets you use integers and booleans interchangeably, because they're really the same type. In Java, they're two completely separate types, and you can't use one where it expects you to use the other. Doing it that way won't really make any difference to how the program runs, but Lakie's right that it's usually considered the neatest way of writing it.

[Steve]

Java is stongly typed, so 1 is not equivalent to true, as it would be in many scripting languages like Perl or Python.
while (true) { } would work just dandily, but I don't see any problem with for (;;) { }.

Backspace characters only work in some console environments those which are tty-like (teletype). This includes the usual console, but not a file. And apparently not eclipse.. System.out should have a function to check this, so you can alter your output accordingly.

[denny577]

In C++ at least, "while (1)" would be much better

When I try that it says "cannot convert from int to boolean", but my version did work fine anyway

If you wanted to do it that way in Java, you'd have to use while (true) { instead of while (1) { , because Java is more strict about type checking than C++ is.

It works thank you
and as for the backspace, it works on the command line, only if I take out the \n it becomes very unstructured in Eclipse when I run it, it prints everything after each other, making it very hard to terminate

[denny577]

Now I'm trying to make a program which saves the key you press into a variable, but the only way I know is getKey() but it says it cannot resolve and I don't know if I should use any imports or which, atm I have java.lang.* and java.util.*. I don't have a clue anymore so if anyone could help me out, I'd be grateful.

[Daan Timmer]

Now I'm trying to make a program which saves the key you press into a variable, but the only way I know is getKey() but it says it cannot resolve and I don't know if I should use any imports or which, atm I have java.lang.* and java.util.*. I don't have a clue anymore so if anyone could help me out, I'd be grateful.

Do you want to read it from the console? or do you want to read it from a KeyListener?
(KeyListener)

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import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

class AFrame extends JFrame{
public AFrame(){
addKeyListener(new KeyListener(){
public void keyPressed(KeyEvent ke){}
public void keyReleased(KeyEvent ke){}
public void keyTyped(KeyEvent ke){}
});
}

(console)

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import java.util.Scanner;

class AClass{
public AClass(){
Scanner in = new Scanner(System.in);
String tmpStr = in.nextLine();
in.close();
//do something with tmpStr;
}
}

sorry for no indention, typed it just in here