Develop Reference

Random generator always amounting to 0 (Java)

I am working through Head First Java, and my Random generator is amounting to 0. Here are my classes:
This is my class with the main method.
public class GameLauncher {
public static void main(String[] args) {
GuessGame game = new GuessGame();
game.startGame();
}
}
This is my player object class:
import java.util.Random;
public class Player {
int number = 0; //Where the guess goes
public void guess() {
//random1 is in GuessGame
Random random2 = new Random();
int number = random2.nextInt(10);
System.out.println("I'm guessing " + number);
}
}
Finally, this is the class where most of the code is happening.
import java.util.Random;
public class GuessGame {
//Guessgame has three instance variables for the three Player objects
Player p1;
Player p2;
Player p3;
public void startGame() {
//Create three Player objects and assign them to the three Player instance variables
p1 = new Player();
p2 = new Player();
p3 = new Player();
//Declare three variables to hold the three guesses the players make
int guessp1 = 0;
int guessp2 = 0;
int guessp3 = 0;
//Declare three variables to hold a true or false based on the player's answer
boolean p1isRight = false;
boolean p2isRight = false;
boolean p3isRight = false;
//Make a "target" number that the players have to guess
Random random = new Random();
//Generate a number between 0 and 9
int targetNumber = random.nextInt(10);
System.out.println("I'm thinking of a number between 0 and 9...");
while (true) {
System.out.println("Number to guess is " + targetNumber);
//Call each player's guess() method
p1.guess();
p2.guess();
p3.guess();
/*
Get each player's guess (the result of their guess() method
running) by accessing the number variable of each player
*/
guessp1 = p1.number;
guessp2 = p2.number;
guessp3 = p3.number;
System.out.println("Player one guessed " + guessp1);
System.out.println("Player two guessed " + guessp2);
System.out.println("Player three guessed " + guessp3);
/*
Check each player's guess to see if it matches the target number. If a player is right, then set that player's variable to be true (remember, we set it false by default)
*/
if (guessp1 == targetNumber) {
p1isRight = true;
}
if (guessp2 == targetNumber) {
p2isRight = true;
}
if (guessp3 == targetNumber) {
p3isRight = true;
}
//If player one OR player two OR player three is right... (the || operator means OR)
if (p1isRight || p2isRight || p3isRight) {
System.out.println("We have a winner!");
System.out.println("Player one got it right? " + p1isRight);
System.out.println("Player two got it right? " + p2isRight);
System.out.println("Player three got it right? " + p3isRight);
System.out.println("Game is over.");
break; //Game over, so break out of the loop
}
else {
//We must keep going because nobody got it right!
System.out.println("Players will have to try again.");
} //end if/else
} //end loop
} //end method
} //end class
I am new to these forums, so if I did something wrong please let me know :)
Does anyone know why this isn't working?
Thanks,
Lyfe

You are storing random number in local variable and you think you set it in instance variable
at line
int number = random2.nextInt(10);
change it to
this.number = random2.nextInt(10);
that atleast solves stated problem.
Also See
Java Variables

Java / Creating hi/low game using multiple methods, stuck at returning no. of guesses

I'm creating a high/low guessing game as part of a study assignment, and the part im stuck at is getting the amount of guesses returned to the main method. We have specifically been told that the main method has to print the number of guesses, while the method "playGame" actually does the playing.
There's more to the code, a method called giveReponse that checks if the number is correct or too high/low, but it works as intended. I get "Cannot find symbol" when trying to print how many guesses it took to complete the game.
If it wasn't so important to print it in the main method I'd print the amount in the method playGame, but thats a no-go. What am I doing wrong?
The code looks like this:
public class HiLo {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Welcome to classic guessing game of high/low!");
String difficulty = scan.next();
if (difficulty.equals("easy")) {
playGame(10);
} else if (difficulty.equals("medium")) {
playGame(100);
} else if (difficulty.equals("hard")) {
playGame(1000);
}
System.out.println("You won in" + guesses + "attempts.");
}//EndsMain
public static int playGame(int maxNumber) {
Scanner scan = new Scanner(System.in);
int rannr = (int)(Math.random() * maxNumber) +1;
int answer = rannr;
int guess = 0;
int guesses = 0;
System.out.println("Game is starting...");
do {
guess = scan.nextInt();
guesses ++;
giveResponse(answer, guess);
if (answer == guess) {
break;
}
} while (answer != guess);
return guesses;
} //Ends playGame

Your method playGame( ) is returning a value but since is not assigned to no variable, those returns are getting lost...
additional to that it looks like the code is not complete:
this statement is not going to let you compile:
System.out.println("You won in" + guesses + "attempts.");
because the only guesses variable I see in there is scoped in the playGame method....
do instead something like:
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Welcome to classic guessing game of high/low!");
int guesses = 0;
String difficulty = scan.next();
if (difficulty.equals("easy")) {
guesses = playGame(10);
} else if (difficulty.equals("medium")) {
guesses = playGame(100);
} else if (difficulty.equals("hard")) {
guesses = playGame(1000);
}

The problem is at:
System.out.println("You won in" + guesses + "attempts.");
Since the variable guesses is not defined in the main method, the compiler doesn't know what you are referencing to with that symbol.
But since playGame() returns the number of guesses, I'd recommend something like this:
if (difficulty.equals("easy")) {
System.out.println("You won in" +playGame(10)+ "attempts.");
} else if (difficulty.equals("medium")) {
System.out.println("You won in" +playGame(100)+ "attempts.");
} else if (difficulty.equals("hard")) {
System.out.println("You won in" +playGame(1000)+ "attempts.");
}

Here's a solution that shows how easy it would be to restrict guesses. Not much extra effort or thought:
package games;
import java.util.Random;
import java.util.Scanner;
/**
* HiLo guessing game
* Created by Michael
* Creation date 4/9/2016.
* #link https://stackoverflow.com/questions/36522303/java-creating-hi-low-game-using-multiple-methods-stuck-at-returning-no-of-gu
*/
public class HiLo {
public static void main(String [] args) {
int maxValue = (args.length > 0) ? Integer.parseInt(args[0]) : 100;
int maxGuesses = (args.length > 1) ? Integer.parseInt(args[1]) : 5;
Scanner scanner = new Scanner(System.in);
String answer = "Y";
do {
play(scanner, maxValue, maxGuesses);
System.out.println("Play again? [Y/N]: ");
answer = scanner.next();
System.out.println(String.format("You answered %s; let's play again!", answer));
} while ("Y".equalsIgnoreCase(answer));
}
private static void play(Scanner scanner, int maxValue, int maxGuesses) {
int value = new Random().nextInt(maxValue) + 1;
int numGuesses = 0;
boolean match = false;
do {
System.out.println(String.format("Guess a value between 1 and %d: ", maxValue));
int guess = Integer.parseInt(scanner.next());
if (guess < value) {
System.out.println(String.format("Too low; guess again. (%d guesses left)", (maxGuesses-numGuesses-1)));
} else if (guess > value) {
System.out.println(String.format("Too high; guess again (%d guesses left)", (maxGuesses-numGuesses-1)));
} else {
match = true;
System.out.println(String.format("You got it right in %d guesses! ", numGuesses+1));
break;
}
} while (!match && ++numGuesses < maxGuesses);
if (!match) {
System.out.println(String.format("The correct answer was %d; you're only allowed %d guesses. Better luck next time!", value, maxGuesses));
}
}
}

Calling local variables in other static methods?

I am supposed to write a program that selects a random number between user given constraints, and asks the user to input guesses as to what this number is. The program gives feedback to the user as to whether or not the number is higher or lower than the user's guesses. The number of guesses, the number of games, the total guesses used throughout all of the games, and the lowest number of guesses used in one game are recorded.
These results are printed. The functions that responsible for running the game (playGame()) and the functions responsible for printing these results (getGameResults()) must be in two separate methods.
My problem is, I am not sure how to get the local variables that are modified throughout the course of the method playGame() to the getGameResults() method.
getGameResults() is intended to be called in another method, continuePlayTest(), which tests the user's input to determine whether or not they wish to continue playing the game, so I don't think that calling getGameResults() will work, otherwise this test will not work either. Unless I call continuePlayTest() in playGame(), but continuePlayTest() calls playGame() in its code so that would complicate things.
We can use ONLY the concepts that we've learned. We cannot use any concepts ahead.
So far, we've learned how to use static methods, for loops, while loops, if/else statements and variables. Global variables are bad style, so they cannot be used.
CODE:
public class Guess {
public static int MAXIMUM = 100;
public static void main(String[] args) {
boolean whileTest = false;
gameIntroduction();
Scanner console = new Scanner(System.in);
playGame(console);
}
// Prints the instructions for the game.
public static void gameIntroduction() {
System.out.println("This process allows you to play a guessing game.");
System.out.println("I will think of a number between 1 and");
System.out.println(MAXIMUM + " and will allow you to guess until");
System.out.println("you get it. For each guess, I will tell you");
System.out.println("whether the right answer is higher or lower");
System.out.println("than your guess.");
System.out.println();
}
//Takes the user's input and compares it to a randomly selected number.
public static void playGame(Scanner console) {
int guesses = 0;
boolean playTest = false;
boolean gameTest = false;
int lastGameGuesses = guesses;
int numberGuess = 0;
int totalGuesses = 0;
int bestGame = 0;
int games = 0;
guesses = 0;
games++;
System.out.println("I'm thinking of a number between 1 and " + MAXIMUM + "...");
Random number = new Random();
int randomNumber = number.nextInt(MAXIMUM) + 1;
while (!(gameTest)){
System.out.print("Your guess? ");
numberGuess = console.nextInt();
guesses++;
if (randomNumber < numberGuess){
System.out.println("It's lower.");
} else if (randomNumber > numberGuess){
System.out.println("It's higher.");
} else {
gameTest = true;
}
bestGame = guesses;
if (guesses < lastGameGuesses) {
bestGame = guesses;
}
}
System.out.println("You got it right in " + guesses + " guesses");
totalGuesses += guesses;
continueTest(playTest, console, games, totalGuesses, guesses, bestGame);
}
public static void continueTest(boolean test, Scanner console, int games, int totalGuesses, int guesses, int bestGame) {
while (!(test)){
System.out.print("Do you want to play again? ");
String inputTest = (console.next()).toUpperCase();
if (inputTest.contains("Y")){
playGame(console);
} else if (inputTest.contains("N")){
test = true;
}
}
getGameResults(games, totalGuesses, guesses, bestGame);
}
// Prints the results of the game, in terms of the total number
// of games, total guesses, average guesses per game and best game.
public static void getGameResults(int games, int totalGuesses, int guesses, int bestGame) {
System.out.println("Overall results:");
System.out.println("\ttotal games = " + games);
System.out.println("\ttotal guesses = " + totalGuesses);
System.out.println("\tguesses/games = " + ((double)Math.round(guesses/games) * 100)/100);
System.out.println("\tbest game = " + bestGame);
}
}

If you cannot use "global" variables, I guess your only option is passing parameters when calling the method. If you don't know how to declare and use methods with parameters, I don't know another answer.
EDIT/ADD
After you specified your question, circumstances and posted your code I got a working solution including comments.
public class Guess {
public static int MAXIMUM = 100;
public static void main(String[] args) {
boolean play = true; // true while we want to play, gets false when we quit
int totalGuesses = 0; // how many guesses at all
int bestGame = Integer.MAX_VALUE; // the best games gets the maximum value. so every game would be better than this
int totalGames = 0; // how many games played in total
Scanner console = new Scanner(System.in); // our scanner which we pass
gameIntroduction(); // show the instructions
while (play) { // while we want to play
int lastGame = playGame(console); // run playGame(console) which returns the guesses needed in that round
totalGames++; // We played a game, so we increase our counter
if (lastGame < bestGame) bestGame = lastGame; // if we needed less guesses last round than in our best game we have a new bestgame
totalGuesses += lastGame; // our last guesses are added to totalGuesses (totalGuesses += lastGame equals totalGuesses + totalGuesses + lastGame)
play = checkPlayNextGame(console); // play saves if we want to play another round or not, whats "calculated" and returned by checkPlayNextGame(console)
}
getGameResults(totalGames, totalGuesses, bestGame); // print our final results when we are done
}
// Prints the instructions for the game.
public static void gameIntroduction() {
System.out.println("This process allows you to play a guessing game.");
System.out.println("I will think of a number between 1 and");
System.out.println(MAXIMUM + " and will allow you to guess until");
System.out.println("you get it. For each guess, I will tell you");
System.out.println("whether the right answer is higher or lower");
System.out.println("than your guess.");
System.out.println();
}
// Takes the user's input and compares it to a randomly selected number.
public static int playGame(Scanner console) {
int guesses = 0; // how many guesses we needed
int guess = 0; // make it zero, so it cant be automatic correct
System.out.println("I'm thinking of a number between 1 and " + MAXIMUM + "...");
int randomNumber = (int) (Math.random() * MAXIMUM + 1); // make our random number. we don't need the Random class with its object for that task
while (guess != randomNumber) { // while the guess isnt the random number we ask for new guesses
System.out.print("Your guess? ");
guess = console.nextInt(); // read the guess
guesses++; // increase guesses
// check if the guess is lower or higher than the number
if (randomNumber < guess)
System.out.println("It's lower.");
else if (randomNumber > guess)
System.out.println("It's higher.");
}
System.out.println("You got it right in " + guesses + " guesses"); // Say how much guesses we needed
return guesses; // this round is over, we return the number of guesses needed
}
public static boolean checkPlayNextGame(Scanner console) {
// check if we want to play another round
System.out.print("Do you want to play again? ");
String input = (console.next()).toUpperCase(); // read the input
if (input.contains("Y")) return true; // if the input contains Y return true: we want play another round (hint: don't use contains. use equals("yes") for example)
else return false; // otherwise return false: we finished and dont want to play another round
}
// Prints the results of the game, in terms of the total number
// of games, total guesses, average guesses per game and best game.
public static void getGameResults(int totalGames, int totalGuesses, int bestGame) {
// here you passed the total guesses twice. that isnt necessary.
System.out.println("Overall results:");
System.out.println("\ttotal games = " + totalGames);
System.out.println("\ttotal guesses = " + totalGuesses);
System.out.println("\tguesses/games = " + ((double) (totalGuesses) / (double) (totalGames))); // cast the numbers to double to get a double result. not the best way, but it works :D
System.out.println("\tbest game = " + bestGame);
}
}
Hope I could help.

Is it a problem passing the variables between functions? ex:
public static void getGameResults(int games, int totalGuesses, int guesses, int bestGame) {
// implementation
}
Another option, assuming this is all in one class, is using private static memeber variables. They aren't global. Then again, they might be considered 'global' by your teacher for this assignment.

Given that you've only learnt how to use static methods, your only option is to pass the information from function to function via its arguments.

Object Oriented Approach for a simple game

I am working on building a simplified version of this game. The problem states that you can have a computer that is smart or stupid but i have decided that to exclude that feature for now and decided to only go with a computer that picks a random amount of objects. I posted a question earlier and worked on it. (https://softwareengineering.stackexchange.com/questions/244680/object-oriented-design-of-a-small-java-game/244683#244683)
So initially i only had designed one class. But now i have designed 3 classes as stated by the problem. I have a pile class , a player class and a game class (also my main class).
I have so far coded the Pile and Player class. I started coding the Game class aswell however i am stuck now as i dont know how to make the game class interact with the Player and Pile class. I basically determine who's turn it is first and then rotate turns till the pile of objects is complete and declare a winner...I don't know how to make the different classes interact with each other . SO i would highly appreciate if someone can guide me further and help me finish this simple game.
I sincerely apologize if i have asked a bad question. This is my first such program i am doing in java dealing with multiple classes so it is a little confusing. I do not want anyone write code but even mentioning or telling me i should make so and so methods etc will be great !
HERE IS THE CODE I HAVE SO FAR.
PILE CLASS
package Nim;
import java.util.Random;
public class Pile {
private int initialSize;
public Pile() {
}
Random rand = new Random();
public void setPile() {
initialSize = (rand.nextInt(100 - 10) + 10);
}
public void reducePile(int x) {
initialSize = initialSize - x;
}
public int getPile() {
return initialSize;
}
public boolean hasStick() {
if (initialSize > 0) {
return true;
}
else {
return false;
}
}
}
PLAYER CLASS
package Nim;
import java.util.Scanner;
import java.util.Random;
public class Player {
public static final int HUMAN = 0;
public static final int COMPUTER = 1;
private int type;
public Player(int theType) {
type = theType;
}
Scanner in = new Scanner(System.in);
// n is number of marbles left in the pile
public int makeMove(int n) {
int max = n / 2;
int grab;
if (type == HUMAN) {
System.out.println("There are " + n
+ " marbles in total. However you can only"
+ "grab no more than " + max + " marbles");
System.out.println("Please Enter the number of marbles to grab: ");
grab = in.nextInt();
while (grab > max || grab < 0) {
System.out.println("You have entered a illelgal value. Please enter a legal value: ");
grab = in.nextInt();
}
return grab;
}
else {
Random rand = new Random();
grab = (rand.nextInt(n / 2 - 1) + 1);
System.out.println("Computer has grabbed: " + grab + " marbles");
return grab;
}
}
public void updateTurn(int n) {
type = n;
}
}
GAME CLASS (in progress)
package Nim;
import java.util.Scanner;
import java.util.Random;
public class Game {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Random rand = new Random();
System.out.println(welcome());
Pile marbles = new Pile();
Player human = new Player(Player.HUMAN);
Player computer = new Player(Player.COMPUTER);
marbles.setPile();
System.out.println("There are total: " + marbles.getPile()
+ " marbles in the Pile.");
System.out.println("Time for a toin coss to see who goes first!");
System.out.println("Please Select heads(0) or Tails(1): ");
int choice = in.nextInt();
int tossResult = rand.nextInt(2);
boolean playerTurn = false;
boolean computerTurn = false;
if (choice == tossResult) {
System.out.println("You have won the Coin Toss! You will go first!");
human.updateTurn(0);
playerTurn = true;
}
else {
System.out.println("Computer has won the coin toss! Computer will go first");
computer.updateTurn(1);
computerTurn = true;
}
while (marbles.getPile() > 0 && marbles.hasStick()) {
while (playerTurn) {
int removeMarbles = human.makeMove(marbles.getPile());
marbles.reducePile(removeMarbles);
computerTurn = true;
playerTurn = false;
}
while (computerTurn) {
int removeMarbles = computer.makeMove(marbles.getPile());
marbles.reducePile(removeMarbles);
playerTurn = true;
computerTurn = false;
}
}
}
private static String welcome() {
return "Welcome to the Game of Nim";
}
}

So I'm going to take a step back and look at your class diagram.
You have three classes: Pile, Player, and Game. Pile can represent the pile at the center. Game can be the class with the main method that manages everything. And Player? Well, since you're having one Player class for all three (or two) possible states (Human, Dumb, and Smart) it should be pretty easy to implement.
Let's start with Game. It need to contain two instances of Player (human and computer), and an instance of Pile. It also needs to have a loop that goes until the game is over. So let's start to come up with a basic implementation:
Starting with Pile:
private int size;
public Pile(int newSize) {
size = newSize;
}
public boolean takeMarbles(int amount) {
size -= amount;
if (size < 1)
return false;
return true;
}
The constructor is pretty self explanatory. The takeMarbles method is returning false if the player lost, and true if they're still in the game.
Now on to Player:
public static final int HUMAN = 0;
public static final int COMPUTER = 1;
private int type;
public Player(int type) {
this.type = type;
}
Those two static fields may seem a little out of place, but it will come together in a second. On to the Game class:
Pile pile = new Pile(size);
Player human = new Player(Player.HUMAN);
Player computer = new Player(Player.COMPUTER);
Now we have a pile with a certain size, and two players that differ by type. This is how we're using the classes.
Now we need to get the main game loop working. Basically, just add an update() method to Player that depends on it's type (ie prompts for input if player, randomly decides if computer). The update method should return the amount of marbles to take. Then create a loop in the main method in Game. The loop will call update of the player and the computer repeatedly until someone loses (takeMarbles returns false). Then it will break out of the loop and print the output.
This is the basic idea, good luck and feel free to ask more questions!

Cows and Bulls game

I'm working on a cows and bulls game with two different classes:
The first class looks like this:
import java.util.*;
import java.util.Scanner;
public class CowsAndBulls {
int UserNumber=0;
int CompNumber=0;
int bulls=0;
int cows=0;
Scanner input = new Scanner(System.in);
public void getUserNumber() {
System.out.println("Please enter your guess!");
int UserValue=input.nextInt();
UserNumber=UserNumber+ UserValue;
System.out.println("Your guess is : " + UserNumber);
}
public void getCompNumber() {
Random generator= new Random();
int pickedNumber=generator.nextInt(10000) + 1000;
CompNumber =CompNumber+ pickedNumber;
System.out.println("The computer has guessed : " + CompNumber );
}
}
It just generates a random number for the computer and asks the user to input their guess.
I'm having a lot of trouble with my play class, specifically, I can't get my while loop to run,
public class CowsAndBullsPlay {
public void play() {
int GuessCount=0;
int UserNumber = 0;
int CompNumber = 0;
int cows = 0;
int bullcount=0;
int cowcount=0;
int bulls = 0;
Boolean GameEnds;
GameEnds=false;
while (GameEnds=false) {
CowsAndBulls user= new CowsAndBulls();
user.getUserNumber();
CowsAndBulls comp= new CowsAndBulls();
comp.getCompNumber();
String UserString=String.valueOf(UserNumber);
String CompString=String.valueOf(CompNumber);
String U=UserString;
String C=CompString;
for (int i=0; i<4; i++)
for (int k=i+1; k<4; k++) {
if(U.charAt(i)==C.charAt(k)) {
bullcount ++;
bulls=bulls + bullcount;
}
else if(U.contains(C.charAt(i) + U)) {
//for (int v=0; v<4; v++)
//for (int j=0; j<4; j++) {
cowcount ++;
cows=cows + cowcount;
}
GuessCount++;
}
if (bulls==4) {
GameEnds= true;
System.out.println("Congratulations!");
System.out.println("it took you:" + GuessCount);
}
else {
System.out.println("cows: " + cows);
System.out.println("Bulls:" + bulls);
}
}
}
}
It's supposed to check for cows and then check for bulls, then if bulls is not equal to four, the loop should reiterate--calling the first two methods that ask for user input and ask computer to randomly generate a number and then guesscount should keep track of loop iterations.
The code compiles, but it just won't run the while loop
here is my tester class:
public class CowsAndBullsTester {
public static void main(String[] args) {
int bears = 0;
int cows = 0;
Boolean GameEnds = false;
System.out.println("welcome to Cows Versus Bulls death match!");
CowsAndBulls user= new CowsAndBulls ();
user.getUserNumber();
System.out.println("Now the computer will pick a number!");
CowsAndBulls comp= new CowsAndBulls ();
comp.getCompNumber();
System.out.println("Let's see how you did!");
CowsAndBullsPlay game= new CowsAndBullsPlay();
game.play();
}
}
Really appreciate any help. I'm sure there's some stupid mistake, I'm just not sure what. This is only my third assignment and I'm having some trouble figuring out what's wrong on my own :)
thanks!

You need to change while (GameEnds=false) to while (GameEnds==false).
The first is an assignment, while the second is a comparison. So in the first, false will be assigned to GameEnds, and then GameEnds will evaluate to false for your while condition, meaning that the loop will never enter.
Also, see #AndrewMao's comment below. Generally, you will see booleans used in conditions directly, with or without negation (!), because they already hold truth values and a further comparison is redundant.
Small side note: you may want to rename your variable in camelCase for clarity.