question: public void diffEquals ( ) { double [ ] col = null ; for ( int i = 0 ; i < A . length ; i ++ ) { col = new double [ A [ i ] . length - 1 ] ; for ( int j = 1 ; j < A [ i ] . length ; j ++ ) col [ j - 1 ] = Math . abs ( A [ i ] [ j ] - A [ i ] [ j - 1 ] ) ; A [ i ] = col ; } n -- ; }
target:  X.diffEquals() calculates differences between adjacent columns of this matrix. Consequently the size of the matrix is reduced by one. The result is stored in this matrix object again.