How to set default value of a 2D array?

Hi!
When I used to use 2D fixed arrays (int[][], or int[] for that matter) it was always a bit annoying setting the values. Like default boolean state in an array is false. Is it possible to set it to something else without using

int w = 10, h = 10, defaultValue = 123;
int grid[][] = new int[w][h];
for(int i = 0;i < w; i++) for(int j = 0; j < h; j++) grid[i][j] = defaultValue;

Nope! If it’s primitive type default value is 0 and false for boolean.
For non-primitive types default value is null.
docs.Oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

3 Likes


// int w = 10, h = 10,
final int defaultValue = 123;

int grid[][] = {
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}, 
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}, 
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}, 
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}, 
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}, 
  { defaultValue, defaultValue, defaultValue, defaultValue, defaultValue}
};

size(660, 660); 

for (int i = 0; i < grid.length; i++) {
  for (int j = 0; j < grid[i].length; j++) {
    text(grid[i][j], 
      i*39+40, j*18+40);
  }
}

:wink:

is there really no such thing as boolean abc[] = new boolean[9](true)?
except for ={true,true,true,true,true,...}

1 Like

Well, most we can do in Java is use Arrays.fill():
docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/util/Arrays.html#fill(byte[],byte)

final boolean[] abc = new boolean[9];
java.util.Arrays.fill(abc, true);

println(str(abc));
exit();

For your previous 2D array we can shorten its initialization loop using Arrays.fill() this way:

static final int ROWS = 3, COLS = 2, DEFAULT = 123;
final int[][] grid = new int[ROWS][COLS];

{
  for (final int[] row : grid)  java.util.Arrays.fill(row, DEFAULT);
}

void setup() {
  for (final int[] row : grid)  println(str(row));
  exit();
}
2 Likes

Hi!
Thank you for showing me this!

I just went through several java documentation pages and saw a “0x123a” example. It is supposed to be hex number. Is there any other 0x value or something like 2x010101?

Use prefix 0b for binary literals: static final int DEFAULT = 0b010101; // 21

are there any others? would 0d100 mean 100 in decimal?

Look for section “Integer Literals” for all available Java prefixes on my 1st posted link:
docs.Oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

However it seems like they’ve skipped the octal number system.
For octal literals just prefix them w/ 0 like this: 0400 = 256.