question: private int [ ] joinMap ( int [ ] a , int [ ] b ) { if ( a == null ) { return b ; } if ( b == null ) { return a ; } int [ ] result = new int [ a . length + b . length ] ; System . arraycopy ( a , 0 , result , 0 , a . length ) ; System . arraycopy ( b , 0 , result , a . length , b . length ) ; return result ; }
target:  Joins two map arrays (int[]) together.