System.out.println , System.err.println

Question

I have this code:

 System.err.print("number of terms =   ");
 System.out.println(allTerms.size());
 System.err.print("number of documents =   ");
 System.out.print("number of documents =   ");

I think the results should be as this:

number of terms = 10
number of documents =1000

but the results was

10
1000
number of terms =   number of documents =

Why, and how to solve it?

Have you tried using the same output stream for all of them? System.out or System.err. — user845279, May 07 '12 at 19:24

score 9 · Answer 1 · answered May 07 '12 at 19:23

9

The streams out and err are independent.

To get the desired output you must flush the streams or just use just one stream for all outputting.

answered May 07 '12 at 19:23

Christopher Oezbek

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i need the output to be red so i used system.err , how can i make it red please – William Kinaan May 07 '12 at 19:35
You _must_ write both outputs to the same stream. Either use `System.err` for both, or use `System.out` for both. – Louis Wasserman May 07 '12 at 19:42
Did you try flushing the streams? After each call to print? – Christopher Oezbek May 07 '12 at 19:54

score 3 · Accepted Answer · answered May 07 '12 at 19:22

3

To solve it

System.out.print("number of terms = ");

System.out.println(allTerms.size());

System.out.print("number of documents = ");

System.out.print("number of documents = ");

System.out.println -> Sends the output to a standard output stream. Generally monitor.

System.err.println -> Sends the output to a standard error stream. Generally monitor.

answered May 07 '12 at 19:22

Habib

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i need to use system.err cos it gives me a red color – William Kinaan May 07 '12 at 19:24
@WilliamKinaan, then use System.err, but for all – Habib May 07 '12 at 19:27
@WilliamKinaan, or try System.out.println("\u001B31;1mhello world!"); to print in red, not tested though – Habib May 07 '12 at 19:30
1

http://stackoverflow.com/questions/1448858/how-to-color-system-out-println-output – Habib May 07 '12 at 19:40
Did you try flushing the streams after each print call? – Seph May 09 '12 at 05:23

score 3 · Answer 3 · answered May 07 '12 at 19:32

System.out.print ("He");  
System.out.print ("llo ");  
System.out.println ("World");

is guaranteed to print "Hello World", but

System.out.print ("He");  
System.err.print ("llo ");  
System.out.println ("World");

might print "llo He World" or "HeWorld llo". They are 2 different streams.

score 2 · Answer 4 · answered May 07 '12 at 19:22

2

System.err.print() prints to stderr which may not show up in the console. Switch them to System.out.print()

answered May 07 '12 at 19:22

Timothy Swartz

194
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score 2 · Answer 5 · edited May 23 '17 at 11:56

2

System.err and System.ou are two different things. With System.out you are writign to stdout with system.err you are writing to stderr.

Try to replace System.err with System.out and you see that your problem disappear.

Then you have to replace:

System.err.print("number of terms = ");

with

System.out.print("number of terms = ");

To change the color of the println check that question: How to color System.out.println output?

edited May 23 '17 at 11:56

Community

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answered May 07 '12 at 19:23

Ivan

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ok , but how to make system.out as a red color , cos i used system.err just cos it gives me a red color – William Kinaan May 07 '12 at 19:29

score 1 · Answer 6 · answered May 07 '12 at 19:41

After every print* statement, use respective stream's flush method. That may give you desired out put.

System.err.print("number of terms =   "); System.err.flush();  
System.out.println(allTerms.size()); System.out.flush();  
System.err.print("number of documents =   "); System.err.flush();  
System.out.print( numberOfDocuments ); System.out.flush();

Will result in:

number of terms =   10
number of documents =   1000

Hoping you are doing a console app, and as you expected err prints in red.

score 0 · Answer 7 · edited May 29 '12 at 21:38

0

This might be the reason: err and out both have a different ouptput stream which will print according to the sequence of getting access to the console.

edited May 29 '12 at 21:38

Peter Mortensen

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answered May 09 '12 at 04:55

RTA

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System.out.println , System.err.println

7 Answers7