2D Arrays: Creation and Access

AP Computer Science A· difficulty 4/5

int[][] m = {{1, 2, 3}, {4, 5, 6}};
int sum = 0;
for (int r = 0; r <= m.length; r++) {
    for (int c = 0; c < m[r].length; c++) {
        sum += m[r][c];
    }
}
System.out.println(sum);

What is the result?

A
$15$
B
$6$
C
$21$
D
$ArrayIndexOutOfBoundsException$
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Explanation

The off-by-one r <= m.length allows r to reach 2, so m[r].length attempts to access m[2] which does not exist (only 2 rows). This throws ArrayIndexOutOfBoundsException. This is the classic bounds-check bug.

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