java - How to free memory in 2-D array -

i have long code. logic follows: have 2-d array in java. so, have values inside locations: [0][0], [0][1], [0][2] , values in:[1][0], [1][1], [1][2]. @ point, made comparisons, , done first row. want free memory of: [0][0], [0][1], [0][2] , move next locations [2][0], [2][1], [2][2].

how can this. can not overwrite [0][0], [0][1], [0][2],my code programmed move next row [2][0], [2][1], [2][2] faced memory constraints , want free memory first row [0][0], [0][1], [0][2] not need more. need current row , previous make comparison. so, want delete first row whenever finish comparison.

update: tried assign null unused array locations following:

for (int f = 0; f <= capacity; f++)                       {                            table[f][i-2] = (integer) null;                         }  

my array of type int , need last 2 columns. first 1 not needed once move 1 more position forward. when applied above code assign null, got:

java.lang.nullpointerexception 

set null each reference in row

for (int = 0; < arr.length; i++) {      arr[0][i] = null;   }  

arr should array of references, not primal types

edit
primal types (e.g. int) can use wrapper-class (e.g. java.lang.integer instead of int : integer[][] instead of int[][])

edit2
equivalent previous loop is:

arr[0] = new integer[arr.length]; 

array new integer[arr.length] contains null values