For each question: read the code, trace on paper, select your answer. Feedback appears immediately. Target: 7/10 or higher means you are exam-ready on 2D arrays.
Score: 0 / 10
1.
int[][] grid = {{1,2,3},{4,5,6},{7,8,9}};
int result = 0;
for (int r = 0; r < grid.length; r++)
{
result += grid[r][r];
}
System.out.println(result);
What is printed?
2.
int[][] m = {{5,3,8},{2,7,4},{9,1,6}};
int val = m[0][0];
for (int r = 0; r < m.length; r++)
{
for (int c = 0; c < m[r].length; c++)
{
if (m[r][c] < val)
{
val = m[r][c];
}
}
}
System.out.println(val);
What is printed?
3.
int[][] t = {{1,2},{3,4},{5,6}};
System.out.println(t.length + " " + t[0].length);
What is printed?
4.
int[][] p = {{10,20,30},{40,50,60}};
int s = 0;
for (int c = 0; c < p[0].length; c++)
{
s += p[1][c];
}
System.out.println(s);
What is printed?
5. The following code is intended to print the elements of column 0, but it contains an error.
for (int c = 0; c < grid[0].length; c++)
{
System.out.println(grid[c][0]);
}
What is the error?
6.
int[][] d = {{1,2,3,4},{5,6,7,8},{9,10,11,12}};
int count = 0;
for (int r = 0; r < d.length; r++)
{
for (int c = 0; c < d[r].length; c++)
{
if (d[r][c] % 3 == 0)
{
count++;
}
}
}
System.out.println(count);
What is printed?
7.
int[][] g = {{1,2},{3,4},{5,6},{7,8}};
for (int r = 0; r < g.length; r++)
{
for (int c = 0; c <= r; c++)
{
System.out.print(g[r][c] + " ");
}
System.out.println();
}
What is printed? (Note: g has 4 rows and 2 columns)
8. Which of the following correctly replaces every element in a 2D array with its absolute value?
9.
String[][] w = {{"A","B"},{"C","D"}};
System.out.println(w[1][0] + w[0][1]);
What is printed?
10. A 2D array has 6 rows and 4 columns. A method uses grid[0].length as the outer loop bound and grid.length as the inner loop bound. What happens?
❓ Frequently Asked Questions
How many 2D array questions are on the AP CSA exam?
Expect 8-12 MCQ involving 2D arrays plus the entire FRQ 4. Unit 4 is 30-40% of the exam, and 2D arrays are a major component of that weight.
What makes these questions hard?
These questions use non-obvious variable names, require multi-step tracing through nested loops, and include common traps like row/column confusion and off-by-one errors at matrix boundaries.
About the Author: Tanner Crow has 11+ years of AP Computer Science teaching experience, 1,845+ verified tutoring hours, and a 5.0 rating. His students score 5s at over double the national rate.
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