AP CSA String Manipulation and 2D Arrays

Question 1

Which method returns the number of characters in a String in Java?

Accepted Answer

length()

Answer

The String.length() method returns the number of characters (including spaces) in the string.

Question 2

What does `str.substring(2, 5)` return for `str = "ABCDEFG"`?

Accepted Answer

"CDE"

Answer

substring(2,5) returns characters from index 2 up to but not including index 5, giving 'C','D','E' → "CDE".

Question 3

What does `str.charAt(0)` return for `str = "Hello"`?

Accepted Answer

'H'

Answer

charAt(0) returns the char at index 0, which is 'H' — a primitive char, not a String.

Question 4

How do you compare two Strings for equal content in Java?

Accepted Answer

str1.equals(str2)

Answer

The equals() method compares String content; using == compares object references, which may give unexpected results for Strings.

Question 5

What does `str.indexOf("lo")` return for `str = "Hello"`?

Accepted Answer

3

Answer

indexOf returns the starting index of the first occurrence of the substring; "lo" starts at index 3 in "Hello".

AP CSA - Advanced Placement Computer Science A Practice Test