How to delete stuff printed to console by System out println

Question

In a Java application I m using some calls to System out println    Now I want to find a way to programmatically delete this stuff   I couldn t find any solution with google  so are there any hints

User · Answer

The easiest ways to do this would be   System out println   f     System out println   u000c

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To clear the Output screen  you can simulate a real person pressing CTRL   L  which clears the output   You can achieve this by using the Robot   class  here is how you can do this   try           Robot robbie   new Robot            robbie keyPress 17      Holds CTRL key          robbie keyPress 76      Holds L key          robbie keyRelease 17      Releases CTRL key          robbie keyRelease 76      Releases L key        catch  AWTException ex            Logger getLogger LoginPage class getName    log Level SEVERE  null  ex

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I am using blueJ for java programming  There is a way to clear the screen of it s terminal window  Try this -  System out print    f      this will clear whatever is printed before this line  But this does not work in command prompt

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I ve found that in Eclipse Mars  if you can safely assume that the line you replace it with will be at least as long as the line you are erasing  simply printing   r   a carriage return  will allow your cursor to move back to the beginning of the line to overwrite any characters you see  I suppose if the new line is shorter  you can just make up the different with spaces   This method is pretty handy in eclipse for live-updating progress percentages  such as in this code snippet I ripped out of one of my programs  It s part of a program to download media files from a website       URL url new URL link       HttpURLConnection connection  HttpURLConnection url openConnection        connection connect        if connection getResponseCode    HttpURLConnection HTTP OK                throw new RuntimeException  Response   connection getResponseCode        connection getResponseMessage     on url   link             long fileLength connection getContentLengthLong        File newFile new File ROOT DIR link substring link lastIndexOf             try InputStream input connection getInputStream            OutputStream output new FileOutputStream newFile                  byte   buffer new byte 4096           int count input read buffer           long totalRead count          System out println  Writing   url   to   newFile      fileLength   bytes             System out printf    2f      double totalRead  double fileLength  100 0           while count  -1                        output write buffer 0 count               count input read buffer               totalRead  count              System out printf   r  2f      double totalRead  double fileLength  100 0                     System out println   nFinished index   INDEX

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I found a solution for the wiping the console in an Eclipse IDE  It uses the Robot class  Please see code below and caption for explanation      import java awt AWTException     import java awt Robot     import java awt event KeyEvent      public void wipeConsole   throws AWTException          Robot robbie   new Robot              shows the Console View         robbie keyPress KeyEvent VK ALT           robbie keyPress KeyEvent VK SHIFT           robbie keyPress KeyEvent VK Q           robbie keyRelease KeyEvent VK ALT           robbie keyPress KeyEvent VK SHIFT           robbie keyPress KeyEvent VK Q           robbie keyPress KeyEvent VK C           robbie keyRelease KeyEvent VK C              clears the console         robbie keyPress KeyEvent VK SHIFT           robbie keyPress KeyEvent VK F10           robbie keyRelease KeyEvent VK SHIFT           robbie keyRelease KeyEvent VK F10           robbie keyPress KeyEvent VK R           robbie keyRelease KeyEvent VK R           Assuming you haven t changed the default hot key settings in Eclipse and import those java classes  this should work

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I have successfully used the following    Before public void dontPrintExceptions            get rid of the stack trace prints for expected exceptions     System setErr new PrintStream new NullStream          NullStream lives in the import com sun tools internal xjc util package so might not be available on all Java implementations  but it s just an OutputStream  should be simple enough to write your own

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There are two different ways to clear the terminal in BlueJ  You can get BlueJ to automatically clear the terminal before every interactive method call  To do this  activate the  Clear screen at method call  option in the  Options  menu of the terminal  You can also clear the terminal programmatically from within your program  Printing a formfeed character  Unicode 000C  clears the BlueJ terminal  for example   System out print   u000C

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You could print the backspace character  b as many times as the characters which were printed before   System out print  hello    Thread sleep 1000      Just to give the user a chance to see  hello   System out print   b b b b b    System out print  world      Note  this doesn t work flawlessly in Eclipse console in older releases before Mars  4 5   This works however perfectly fine in command console  See also How to get backspace  b to work in Eclipse  39 s console

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For intellij console the 0x08 character worked for me   System out print  char  8

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Just to add to BalusC s anwswer     Invoking System out print   b  b   repeatedly with a delay gives an exact same behavior as when we hit backspaces in  Windows 7 command console   Java 1 6

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BalusC answer didn t work for me  bash console on Ubuntu   Some stuff remained at the end of the line  So I rolled over again with spaces  Thread sleep   is used in the below snippet so you can see what s happening   String foo    the quick brown fox jumped over the fence   System out printf foo   try  Thread sleep 1000    catch  InterruptedException e     System out printf   s   mul   b   foo length      try  Thread sleep 1000    catch  InterruptedException e     System out printf   s   mul      foo length      try  Thread sleep 1000    catch  InterruptedException e     System out printf   s   mul   b   foo length        where mul is a simple method defined as   private static String mul String s  int n        StringBuilder builder   new StringBuilder        for  int i   0  i  lt  n   i            builder append s       return builder toString         Guava s Strings class also provides a similar repeat method

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You could use cursor up to delete a line  and erase text  or simply overwrite with the old text with new text   int count   1   System out print String format   033  dA  count       Move up System out print   033 2K       Erase line content   or clear screen  System out print String format   033 2J       This is standard  but according to wikipedia the Windows console don t follow it   Have a look  http   www termsys demon co uk vtansi htm

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System out is a PrintStream  and in itself does not provide any way to modify what gets output  Depending on what is backing that object  you may or may not be able to modify it  For example  if you are redirecting System out to a log file  you may be able to modify that file after the fact  If it s going straight to a console  the text will disappear once it reaches the top of the console s buffer  but there s no way to mess with it programmatically   I m not sure exactly what you re hoping to accomplish  but you may want to consider creating a proxy PrintStream to filter messages as they get output  instead of trying to remove them after the fact

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this solution is applicable if you want to remove some System out println   output  It restricts that output to print on console and print other outputs      PrintStream ps   System out  System setOut new PrintStream new OutputStream         Override    public void write int b  throws IOException          System out println  It will not print       To again enable it  System setOut ps    System out println  It will print

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Clearing screen in Java is not supported  but you can try some hacks to achieve this   a  Use OS-depends command  like this for Windows   Runtime getRuntime   exec  cls      b  Put bunch of new lines  this makes ilusion that screen is clear   c  If you ever want to turn off System out  you can try this   System setOut new PrintStream new OutputStream          Override public void write int b  throws IOException

[java] How to delete stuff printed to console by System.out.println()?

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