question: public static double [ ] expandArrayD ( int bufferSize , double [ ] currentArray ) { if ( currentArray == null ) { return new double [ bufferSize * 3 ] ; } int length = currentArray . length ; double [ ] ret = new double [ length + bufferSize * 3 ] ; System . arraycopy ( currentArray , 0 , ret , 0 , length ) ; return ret ; }
target:  Create an array to hold double data for 3d polygons and lines.