What happens to "System.out.println()" in executable jar?

Question

Suppose I've created an executable jar from a code where I have used

System.out.println()

When we run the executable jar, there is no console. So, what happens to this line? How does java handle this situation?

EDIT 01:

NOTE: The situation is when I don't use a console to run the jar nor associate any console with it anyhow.

EDIT 02: Making things clearer:

I know that nothing will be printed anywhere as there is no console..! I want to know how java handle this line in this case? Is this line omitted when generating the bytecode for a executable jar? Or is this line just overlooked when there is no console? Or anything...

Answer 1

There's nothing special about running code in an executable jar file. If you run it from a console, e.g. with java -jar foo.jar the output will still go to the console.

If you run the code in some way that doesn't attach a console - such as javaw on Windows, which is the default program associated with executable jar files - then the output won't go anywhere. It won't cause any errors - the text will just be lost.

Note that in that case, if you use System.console() instead, that will return null. So:

System.out.printf("Foo%n"); // No problem. Goes nowhere.
System.console().printf("Foo%n"); // Would throw a NullPointerException.

Answer 2

The output is omitted, as long as you do not run your application from a console window (java -jar executable.jar). Furthermore, you can configure your Java installation such, that a console windows is launched as soon as you start a Java application. Output will be written to the JVM's console window then. You can find an article How do I enable and view the Java Console? on the official Java web site.