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Change to the directory that contains the bin directory and enter:
java -classpath ./bin com.test.Main myinputfile.txt myoutputfile.txt sort

That directory should contain the myinputfile.txt file.

With the command line:
java -classpath ./bin com.test.Main myinputfile.txt myoutputfile.txt sort
The bin directory needs to be in the current directory
and the com directory needs to be in the bin...