AP CSA String Manipulation and 2D Arrays 2

Question 1

What does `str.toUpperCase()` do?

Accepted Answer

Returns a new String with all characters converted to uppercase

Answer

toUpperCase() returns a new String with all alphabetic characters converted to uppercase; Strings in Java are immutable so the original is unchanged.

Question 2

How do you access the element in row 2, column 3 of a 2D array called `grid`?

Accepted Answer

grid[2][3]

Answer

2D array elements are accessed with [row][column] syntax; grid[2][3] accesses row 2 (third row), column 3 (fourth column).

Question 3

What nested loop structure traverses all elements of a 2D array `int[][] m` with r rows and c columns?

Accepted Answer

for(int i=0;i<m.length;i++) for(int j=0;j<m[i].length;j++)

Answer

The outer loop uses m.length for rows and the inner loop uses m[i].length for columns, correctly visiting every element.

Question 4

What does `str.substring(3)` return for `str = "JavaCode"`?

Accepted Answer

"aCode"

Answer

substring(3) returns all characters from index 3 to the end; J(0),a(1),v(2),a(3)Code → "aCode".

Question 5

What is the result of `"5" + 3 + 2` in Java?

Accepted Answer

"532"

Answer

Java evaluates left to right: "5"+3 is String concatenation giving "53", then "53"+2 gives "532" — not arithmetic.

AP CSA - Advanced Placement Computer Science A Practice Test