question: private double [ ] concatenateSamples ( final double [ ] x , final double [ ] y ) { final double [ ] z = new double [ x . length + y . length ] ; System . arraycopy ( x , 0 , z , 0 , x . length ) ; System . arraycopy ( y , 0 , z , x . length , y . length ) ; return z ; }
target:  Concatenate the samples into one array.