Question

Write an application that plays “guess the number” as follows: Your program chooses the number to be guessed by selecting a random integer in the range 1 to 1000. The application displays the prompt Guess a number between 1 and 1000. The player inputs a first guess. If the player's guess is incorrect, your program should display Too high. Try again. or Too low. Try again. to help the player “zero in” on the correct answer. The program should prompt the user for the next guess. When the user enters the correct answer, display Congratulations. You guessed the number!, and allow the user to choose whether to play again. [Note: The guessing technique employed in this problem is similar to a binary search, which is discussed in Chapter 19, Searching, Sorting and Big O.]

Short answer

Initialize the application, prompt the user to guess, process the guess while providing high or low hints, congratulate upon correct guess, and offer to restart the game.

Step-by-step solution

Initialize the Application

Begin by importing the necessary libraries (random) and initializing variables. Set up a loop to generate a random number within the specified range (1 to 1000) using random.randint(1, 1000). Also, prepare a variable to store the user's guess.

Prompt User for Initial Guess

Display a message asking the user to guess a number, such as 'Guess a number between 1 and 1000.' Read the player's guess using an input function and convert this guess into an integer for comparison.

Process the Guess

Compare the user's guess with the generated random number. If the guess is too high, display 'Too high. Try again.' If the guess is too low, display 'Too low. Try again.' Use a while loop to continually ask for another guess until the correct number is guessed.

User Guesses Correctly

When the user guesses the number correctly, display 'Congratulations. You guessed the number!' Exit the loop that is asking for guesses.

Ask User to Play Again

Ask the user if they want to play again. This can be a simple yes/no prompt. If they choose to play again, restart the game by generating a new random number and repeating the process. If they choose not to play again, end the application.

Key concepts

Control statements in Java

Control statements in Java are crucial for guiding the flow of a program's execution. They enable the program to make decisions based on certain conditions, leading to different outcomes. A typical 'guess the number' game showcases the use of control statements like if, else if, and else to provide feedback to the user.

For instance, after the user makes a guess, an if statement can determine if the guess is too high, too low, or correct. Corresponding actions are then taken based on this evaluation. If the guess is not correct, the user is prompted to try again, illustrating the importance of these control statements in creating an interactive and responsive game.

Java random number generation

Generating random numbers is a common requirement in Java programs, like our 'guess the number' game. In Java, random numbers can be generated using the Random class found in the java.util package. To generate a number within a specific range, such as 1 to 1000, you can use the nextInt method and specify the bound.

Example:

import java.util.Random;
Random rand = new Random();
int numberToGuess = rand.nextInt(1000) + 1;

In this example, nextInt(1000) generates a number from 0 to 999, and adding 1 adjusts the range to 1 to 1000. This ensures that each new game starts with a unique challenge for the player.

Binary search algorithm

The binary search algorithm is a method for finding a specified value within a sorted array. This algorithm is efficient because it reduces the problem size by half with each step, which is known as a logarithmic time complexity, or O(log n).

In the context of a 'guess the number' game, while not an exact implementation of binary search, the concept is similar. The player is encouraged to guess a number in the middle of the range, and each guess divides the range of possible answers in two, narrowing down the correct value with each subsequent guess. Employing this strategy, the player is effectively using a human-driven binary search to arrive at the correct answer quickly.

Java while loops

In Java, a while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. This loop continues to run as long as the condition remains true.

In the 'guess the number' game, a while loop is used to continuously prompt the player for guesses until they find the correct number. It's a perfect example of how while loops can manage repeated actions without unnecessary code repetition. The loop only exits when the user's guess matches the randomly generated number, or if they choose not to play again.

Basic structure of a while loop:

while (condition) {
    // Code to be executed
}

The continuing engagement of the player in the guessing game showcases the practical use of while loops to manage game state and user interactions.