String Method Problems

1. Check if a string contains the substring "is".

2. **Extract the last character from a string.

3. Check if a string starts with the character 'a'.

4. **Count the number of 'e's in a string.

5. Replace all instances of 'y' with 'z' in a string.

6. Get the index of the first space in a string.

7. Convert a string to all uppercase.

8. Check if a string is empty (length is 0).

9. Compare two strings ignoring case.

10. Split a string into an array at each comma.

** - The problem was to extract the last character from a string.

Strings in Java can be thought of as character arrays. We know that arrays are 0-indexed, meaning the first element is at index 0, second at 1 and so on.

To get the last character, we need the index of the last element in the array. Since arrays are 0-indexed, the index of the last element will always be length-1.

The string.length() method returns the total number of characters (length of the internal array). By subtracting 1 from it, we get the index of the last character.

For example, if the string is "Hello":

• length() would return 5

• length()-1 is 4

• The character at index 4 is 'o'

So string.charAt(string.length()-1) lets us cleanly extract the last character without knowing the string length beforehand.

Answers

1. string.contains("is")

2. string.charAt(string.length()-1)

3. string.startsWith("a")

4. string.split("e").length - 1

5. string.replace("y", "z")

6. string.indexOf(" ")

7. string.toUpperCase()

8. string.length() == 0

9. string.equalsIgnoreCase(string2)

10. string.split(",")