How to print an array

Short answer

Arrays.toString() turns an array into a readable string:

void main() {
    int[] numbers = {5, 3, 8};
    IO.println(Arrays.toString(numbers));
}

Output:

[5, 3, 8]

A 2D array

An array of arrays needs Arrays.deepToString():

void main() {
    int[][] grid = {{1, 2}, {3, 4}};
    IO.println(Arrays.deepToString(grid));
}

Output:

[[1, 2], [3, 4]]

A custom format

Join strings with String.join(), and anything else with a stream:

void main() {
    String[] names = {"Anna", "Oleg"};
    double[] prices = {1.5, 20.0};
 
    IO.println(String.join(" / ", names));
    IO.println(Arrays.stream(prices).mapToObj(p -> p + " €").collect(Collectors.joining(", ")));
}

Output:

Anna / Oleg
1.5 €, 20.0 €

A table

A 2D array is easy to print row by row:

void main() {
    int[][] grid = {{1, 2, 3}, {4, 5, 6}};
    for (int[] row : grid) {
        IO.println(Arrays.stream(row).mapToObj(n -> "%3d".formatted(n)).collect(Collectors.joining()));
    }
}

Output:

  1  2  3
  4  5  6

Common mistake

Printing an array directly. Arrays do not override toString(), so you get the type and a hash code:

void main() {
    int[] numbers = {5, 3, 8};
    IO.println(numbers);
}

Output:

[I@1786f9d5

The number after @ will be different for you.

Thanks for reading!

Short answer

A 2D array

A custom format

A table

Common mistake

Functions used in this recipe

Thanks for reading!