AP CSA 2.10 Exercise 1: Walking the Word

Unit 2: Selection and Iteration · Lesson 2.10 · Exercise 1

Walking the Word

Implementing String Algorithms. Write real Java, run it, and submit it to be graded against hidden test cases.

Back to the Lesson 2.10 page All Unit 2 lessons

Why this one is worth doing

A String is walked with charAt and length, index by index. Every String algorithm on the exam is a loop over those two methods, so this is the pattern rather than one of many.

What to write

Read a single word.
Print how many vowels it contains, counting a, e, i, o and u in lower case only.
Print the word reversed.
Print true when the word reads the same forwards and backwards, and false otherwise.
Print the word with every vowel removed.

Your program reads

A single lower case word.

Your program prints

Four lines: the vowel count, the reversed word, the palindrome check and the word with no vowels.

Worked examples

These are the cases you can see. There are more you cannot, and they use different values, so an answer that prints these numbers as constants will fail.

Example 1 input

racecar

Example 1 output

3
racecar
true
rccr

Example 2 input

java

Example 2 output

2
avaj
false
jv

Your answer

Main.java

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    String word = input.next();

    // word.charAt(i) gives one character. word.length() gives how many.
  }
}

Input for the Run button

Run sends whatever is in the input box below. Submitting runs your program against every test case, including hidden ones with different input.

Stuck?

Hint 1

Building the reverse is one line: put each new character in FRONT of what you have so far.

Hint 2

Compare Strings with equals, never with ==. Two Strings that read the same can still be different objects.

Hint 3

A word made only of vowels leaves an empty last line. An empty line is a correct answer here, not a missing one.

Where to go next

Rework the Lesson 2.10 page Pick another Unit 2 lesson

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