java - 2D Tiled Game - Using new bad data -

in 2d tiled game, have problem, when update object 2d array in loop inside (looping in 2d array top left bottom right, row row(like code below)), if program looping @ index (5,6) , need data object under itself, it'll use new data have executed when loop @ (5,5) want use data before start of double loop...

a basical example:

int[][] map = new int[10][10];  for(int x = 0; x < 10; x++) {     for(int y = 0; y < 10; y++)     {          update(x, y, map);     } }  // remember example void update(int x, int y, int[][] m) {     m[x][y] = 0     if(y > 9) { return; }     m[x][y + 1] = 1 } 

it put instantly data "1" @ (x, 10), without considering generate errors...(arrayoutofboundsexception...)

how can make use data of array when don't started double loop yet?

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i know generata arrayoutofboundexecption, , single if can correct done here

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int water = 1; int air = 0; int[][] map = new int[20][20];  void update() {        for(int x = 0; x < 10; x++)     {         for(int y = 0; y < 10; y++)         {             tick(x, y, map);         }     } }  void tick(int x, int y, int[][] m) {     if(y > m.lenght - 1) { return; }     m[x][y] = air;     m[x][y + 1] = water; } 

you saying iterating map row row when doing columns. try looping first y , x.

your update method wrong. y+1 when y = 9 try access map[x][10] throw arrayoutofboundsexception. remember array declared new int[10] has 10 items starting 0 , ending @ position 9.