You can use nested enhanced for loops to read every element in a two-dimensional array. The outer loop reads each row, and the inner loop reads the values in that row.

In this example, you will print a grid of integers, with each row on a separate line.

Source code

public class TwoDimensionalArrayExample {
    void main() {
        int[][] numbers = {
                {1, 2, 3},
                {4, 5, 6},
                {7, 8, 9}
        };

        for (int[] row : numbers) {
            String separator = "";

            for (int number : row) {
                IO.print(separator + number);
                separator = " ";
            }

            IO.println();
        }
    }
}

Explanation

The following declaration creates a two-dimensional array:

int[][] numbers = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
};

In Java, a two-dimensional array is an array whose elements are arrays. Here, numbers contains three rows, and each row contains three integers.

The outer loop reads one row at a time:

for (int[] row : numbers) {

The variable row has the type int[] because each row is an array of integers.

Inside the outer loop, the inner loop reads each number in the current row:

for (int number : row) {
    IO.print(separator + number);
    separator = " ";
}

IO.print() writes output without starting a new line.

The separator variable starts as an empty string for each row. After printing the first number, it becomes a space. This places spaces between the numbers without adding a trailing space.

After the inner loop finishes, the following statement starts a new line:

IO.println();

The outer loop then moves to the next row.

Run the example

Compile and run the file:

javac TwoDimensionalArrayExample.java
java TwoDimensionalArrayExample

Output

1 2 3
4 5 6
7 8 9

Rows with different lengths

The same loop also works when rows contain different numbers of elements. For example, replace the array declaration with:

int[][] numbers = {
        {1, 2},
        {3, 4, 5},
        {6}
};

The output becomes:

1 2
3 4 5
6

Each inner loop processes the elements in its current row, so the rows do not need to have the same length.