Java question

  1. I was curious if anyone knows if there are any methods to do the following in java.

    I'm writing a terminal based program in java, and it will be doing incremental updates. I want to output to the terminal the percentage done, but to replace the last output. For example:

    $>java jprog
    Percent completed...0%
    ...
    $>java jprog
    Percent completed...5%.

    Instead of
    $>java jprog
    Percent completed...0%
    Percent completed...5%
    ...

    I checked the java API's a little, in the PrintStream and OutputStream classes, but couldn't find any methods like that. Anybody know? Thanks.
     
  2. jcsd
  3. chroot

    chroot 10,426
    Staff Emeritus
    Science Advisor
    Gold Member

    Standard output by itself cannot do such a thing. To accomplish this, your Java program actually needs to control the terminal window which shows the output. I suggest you look into implementations of "curses" in Java, for example:

    http://sourceforge.net/projects/javacurses/

    - Warren
     
  4. NateTG

    NateTG 2,537
    Science Advisor
    Homework Helper

    I'm not sure if your Java app can read termcap/terminfo, but it should be possible to send terminal control characters (or maybe backspace) to move the cursor around. (That's what curses does after all.)
     
  5. Hurkyl

    Hurkyl 16,089
    Staff Emeritus
    Science Advisor
    Gold Member

    You could display the information in an alternate manner. For example, you could plot a graph:


    #===1===2===3===4===5===6===7===8===9===#

    And fill up the line below it one character at a time as it progresses. For example, at 22.5%, it would look like:

    #===1===2===3===4===5===6===7===8===9===#
    #===1===2=

    and the cursor is at the end of the second line, ready to display another character as necessary.

    You can make this prettier if you're willing to assume an equal width font.



    If you're willing to assume a *NIX-style environment, the character '\r' is a carriage return (without the line feed) -- it positions the cursor at the beginning of the current line. You could use this to achieve the effect you describe. (Backspace would usually work too, as mentioned)
     
  6. Thanks for all of your suggestions guys, but I did find out a good way to do it:

    '\b'.

    :E

    edit: oops Nate didn't see your reply!
     
  7. Yoss,
    Care to share what you did? I am writing a load tool and I want to print a running throughput average to the console.

    Thanks.
     
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