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10.9. Loop Through Part of a 2D Array

You can loop through just part of a 2D array. For example, you might want to sum all of the values in a given row.

public class Test { public static int getTotalForRow(int row, int[][] a) { int total = 0; for (int col = 0; col < a[0].length; col++) { total = total + a[row][col]; } return total; } public static void main(String[] args) { int[][] matrix = { {1,2,3},{4,5,6} }; System.out.println(getTotalForRow(0,matrix)); } }

You can change the starting value and ending value to loop through a subset of a 2D array.

public class Test { public static int countValues(int value, int[][] a, int rowStart, int rowEnd, int colStart, int colEnd) { int count = 0; for (int row = rowStart; row <= rowEnd; row++) { for (int col = colStart; col <= colEnd; col++) { if (a[row][col] == value) count++; } } return count; } public static void main(String[] args) { int[][] matrix = { {3,2,3},{4,3,6},{8,9,3},{10,3,3} }; System.out.println(countValues(3,matrix,0,2,0,2)); } }

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