difference between System out println and System err println

Question

What is the difference between System out println   and System err println   in Java

User · Answer

Those commands use different output streams. By default both messages will be printed on console but it's possible for example to redirect one or both of these to a file.

java MyApp 2>errors.txt

This will redirect System.err to errors.txt file.

User · Answer

System out s main purpose is giving standard output    System err s main purpose is giving standard error     Look at these  http   www devx com tips Tip 14698  http   wiki eclipse org FAQ Where does System out and System err output go 3F

User · Answer

In Java System out println   will print to the standard out of the system you are using  On the other hand  System err println   will print to the standard error   If you are using a simple Java console application  both outputs will be the same  the command line or console  but you can reconfigure the streams so that for example  System out still prints to the console but System err writes to a file   Also  IDEs like Eclipse show System err in red text and System out in black text by default

User · Answer

It s worth noting that an OS has one queue for both System err and System out  Consider the following code   public class PrintQueue       public static void main String   args            for int i   0  i  lt  100  i                  System out println  out                System err println  err                        If you compile and run the program  you will see that the order of outputs in console is mixed up    An OS will remain right order if you work either with System out or System err only  But it can randomly choose what to print next to console  if you use both of these   Even in this code snippet you can see that the order is mixed up sometimes   public class PrintQueue       public static void main String   args            System out println  out            System err println  err

User · Answer

System out is  quot standard output quot   stdout  and System err is  quot error output quot   stderr   Along with System in  stdin   these are the three standard I O streams in the Unix model  Most modern programming environments  C  Perl  etc   support this model  The standard output stream is used to print output from  quot normal operations quot  of the program  while the error stream is for  quot error messages quot   These need to be separate -- though in most cases they appear on the same console  Suppose you have a simple program where you enter a phone number and it prints out the person who has that number  If you enter an invalid number  the program should inform you of that error  but it shouldn t do that as the answer  If you enter  quot 999-ABC-4567 quot  and the program prints an error message  quot Not a valid number quot   that doesn t mean there is a person named  quot Not a valid number quot  whose number is 999-ABC-4567  So it prints out nothing to the standard output  and the message  quot Not a valid number quot  is printed to the error output  You can set up the execution environment to distinguish between the two streams  for example  make the standard output print to the screen and error output print to a file

User · Answer

this answer most probably help you it is so much easy System err and System out both are the same both are defined in System class as reference variable of PrintStream class as public final static PrintStream out   null   and  public final static PrintStream err   null   means both are ref  variable of PrintStream class   normally System err is used for printing an error messages  which increase the redability for the programmer    A minor difference comes in both when we are working with Redirection operator

User · Answer

System out println  wassup    refers to when you have to output a certain result pertaining to the proper input given by the user whereas System err println  duh  that s wrong   is a reference to show that the input provided is wrong or there is some other error   Most of the IDEs show this in red color  System err print

[java] difference between System.out.println() and System.err.println()

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