I didn't say yo guys are excluded for ever handing a job. But there is a whole batch people coming out with com Sci degree every year, and big companies will look to hire them. It is getting harder...
Only promising way to get in programmer field nowadays is to attend 4 yrs college. It won't happen overnight, forget about focused courses - they make money to ones who teach them.
threads make sense only if you have long task that is cpu or other resource intensive, doesn't matter of the size of code. usually it makes sense to put UI in one thread and long actions in others.
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Please don't treat Java as C. It is not low-level procedural language, it is exact opposite of that. You can't see connection to CPU or RAM from Java as you would with C.
if you have JAR build you can use
java -jar your_file test.txt >> output.txt
or if you have compiled class files
java classfile.class test.txt >> output.txt
putting in hash map puts reference to original object, not deep copy of it, so any changes to object itself will propagate to objects retrieved from hash map