Problem of the Day

Thursday, January 8, 2026

Problem:

A game program is designed so that it prints the message "Let's go!" if the user wants to play again. The String variable playAgain has a value of "y" if the user wants to play the game again. The programmer also wants the program to run the game again (and print the message) if playAgain has a value of "" (the empty string). If playAgain doesn't have a value of "y" or "", the program should print the message "Goodbye!". Which of these conditional statements will correctly print the message "Let's go!" based on the value of playAgain?

if (playAgain.substring(0,1).equals("y") || playAgain.length() == 0)
    System.out.println("Let's go!");
else
    System.out.println("Goodbye!");

if (playAgain.length() == 0 || playAgain.substring(0,1).equals("y"))
    System.out.println("Let's go!");
else
    System.out.println("Goodbye!");

if (playAgain.length() != 0 || !playAgain.substring(0,1).equals("n"))
    System.out.println("Let's go!");
else
    System.out.println("Goodbye!");

if (!playAgain.substring(0,1).equals("n") || playAgain.length() != 0)
    System.out.println("Goodbye!");
else
    System.out.println("Let's go!");

Show solution:

The correct answer is b. The challenge here is the variable playAgain may have two different values that should cause the message to be printed, either "y" or "", and using the substring() method to check for a string with a length of 0 produces an error. By checking for the length of the string first, and then checking for the "y", we can avoid this potential issue. If the first boolean condition in the compound boolean expression is evaluated as true, Java doesn't evaluate the second expression, a process known as boolean short-circuiting.

Answers c and d focus on looking for the character "n", which isn't mentioned in the problem statement and shouldn't be used for analysis in the boolean expressions.