java - Copying matrices -

java - Copying matrices -

i have re-create matrix , alter new matrix, don't want alter initial one. represent them arraylist of arraylists. here code

arraylist<arraylist<integer>> tempmatrix = new arraylist<arraylist<integer>>(); for(arraylist<integer> row : matrix) { for(integer index : row) { tempmatrix.get(row).add(index); } }

compiler says it's illegal utilize method purpose. else can copy?

you can re-create whole row, saving lot of trouble:

arraylist<arraylist<integer>> tempmatrix = new arraylist<arraylist<integer>>(); for(arraylist<integer> row : matrix) { tempmatrix.add(new arraylist<integer>(row)); }

java arraylist