What does substring() do when copying a whole String?

What does substring() do when copying a whole String?

• A. It always returns an empty string
• B. It can create another String containing part or all of the original String
• C. It doubles the original String
• D. It returns only the first character

Answer: (B)

substring creates a new String that contains just the characters from the original string within the specified range. It doesn’t change the original string, since strings are immutable. If you copy the whole string, you’d use the full range (start at 0 and go to the string’s length), and you’d get a new String containing all of its characters. More generally, you can pick a smaller range to get just part of it. This behavior is why it’s described as returning a new String containing part or all of the original. It isn’t designed to duplicate the string or to return only the first character unless you request a range that yields exactly that.

substring creates a new String that contains just the characters from the original string within the specified range. It doesn’t change the original string, since strings are immutable. If you copy the whole string, you’d use the full range (start at 0 and go to the string’s length), and you’d get a new String containing all of its characters. More generally, you can pick a smaller range to get just part of it. This behavior is why it’s described as returning a new String containing part or all of the original. It isn’t designed to duplicate the string or to return only the first character unless you request a range that yields exactly that.