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Printing 10 random questions in JAVA

I am tasked with creating a quizz program in Java which asks the user to find the answer to 10 addition / subtraction problems form ( a + b ) or ( a - b) = c, where "a" and "b" are random numbers.
I was able to do the first part where "a" and "b" get randomly generated and the user is told whether or not their answer is correct. I am stuck on how to generate this question 10 times and how to randomly chose whether the operator is "+" or "-". Below is the code I have so far:
import java.util.Scanner;
import java.util.Random;
public class LetsSee{
public static void main(String [] args){
Scanner keyboard = new Scanner(System.in);
int sum = 0;
int userAnswer ;
int check ;
// Random number generating
Random generator = new Random();
int N1 = generator.nextInt(100);
int N2 = generator.nextInt(N1);
System.out.println(" What is the answer to " + N1 + " + " + N2 + " = " );
userAnswer = new Scanner(System.in).nextInt();
// Display if its correct or not
check = N1 + N2;
if(userAnswer == check){
System.out.println("You are correct!");
}
else{
System.out.println(" Sorry, the correct answer is : " + check);
}
}
}
Help would be GREATLY appreciated. Thanks !

So I came up with a quick solution that would look something like this
Random generator = new Random();
int var1 = generator.nextInt(100);
int var2 = generator.nextInt(100);
int choice = generator.nextInt(3);
switch (choice){
case 0:
System.out.println(var1 + " + " + var2);
break;
case 1:
System.out.println(var1 + " - " + var2);
break;
case 2:
System.out.println(var1 + " * " + var2);
break;
case 3:
System.out.println(var1 + " / " + var2);
break;
}
This is just a rough solution, nothing fancy, but hopefully gives you the idea of what you're looking for.
You needed a choice of one of 4 operators, so I've randomly picked a number from 0-3 to get a random operator, which we can then use in a switch to generate a question based on our 2 random numbers

Let me know if this helps. I just added a for loop to ask the user for input 10 times and then built the +/- based off whether a random int was even or odd.
import java.util.Scanner;
import java.util.Random;
public class HelloWorld{
public static void main(String [] args){
Scanner keyboard = new Scanner(System.in);
int sum = 0;
int userAnswer ;
int check ;
// Random number generating
// Ask the user for input 10 times
for (int i = 0; i < 10; i++) {
Random generator = new Random();
int N1 = generator.nextInt(100);
int N2 = generator.nextInt(N1);
int N3 = generator.nextInt(2);
// if N3 is even use plus, if odd use minus
Boolean plus = N3 % 2 == 0;
// Set a string to either "+" or "-" depending on the value of plus
String plusMinus = plus? "+" : "-";
System.out.println(" What is the answer to " + N1 + plusMinus + N2 + " = " );
userAnswer = new Scanner(System.in).nextInt();
// Display if its correct or not
// Set the answer depending on the value of plus.
check = plus? N1 + N2 : N1 - N2;
if(userAnswer == check){
System.out.println("You are correct!");
}
else{
System.out.println(" Sorry, the correct answer is : " + check);
}
}
}
}

variable doesn't increase when code is executed

Tester is called and executed if the player inputs a certain name.
Variable testerWrong doesnt add one when testerWrong++ is executed
private void Tester(){
int testerTotal;
int testerScore;
int testerWrong;
testerTotal = 0;
testerScore = 0;
testerWrong = 0;
System.out.println("");
System.out.println("Hello tester, you're the designated tester. Would you like to take the quiz? Y/N");
Scanner yesno = new Scanner(System.in);
String YesNo = yesno.next();
if(YesNo.equals("Y") || YesNo.equals("y")){ //This type of code will appear very often
System.out.println("Okay, let's being!"); //if the user input (YesNo) is Y or y then...
}else{
if(YesNo.equals("N") || YesNo.equals("n")){
System.out.println("Okay, maybe some other time");
}else{ //else...
System.out.println("Sorry, i do not recognise what you entered. Please restart the program.");
}
}
System.out.println("");
QUIZ enter = new QUIZ();
enter.e2c();
System.out.println("");
System.out.println("");
System.out.println("");
System.out.println("Question #1");
System.out.println("");
System.out.println("The answer is A");
System.out.println("");
System.out.println(" - A. ");
System.out.println(" - B. ");
System.out.println(" - C. ");
System.out.println(" - D. ");
Scanner testerQ1 = new Scanner(System.in);
String TesterQ1 = testerQ1.next();
if(TesterQ1.equals("A") || TesterQ1.equals("a")){
testerScore++;
System.out.println("Correct! You have answered " + testerScore + " correct and " + testerWrong + " incorrect!");
System.out.println("");
System.out.println("Next Question.");
System.out.println("");
}else{
testerWrong++;
System.out.println("Incorrect! You have answered " + testerScore + " correct and " + testerWrong + " incorrect!");
System.out.println("");
}
Is there a way to make the variable execute without having to add a system output before it?
Thanks

This is not a minimal (way too many print statements) or even complete example (the QUIZ class is not included).
Narrowing your code down to a minimum example:
import java.util.Scanner;
public class Tester {
public static void main(String args[]) {
int testerScore = 0;
int testerWrong = 0;
System.out.println("The answer is A");
Scanner scanner = new Scanner(System.in);
String answer = scanner.next();
if (answer.equals("A") || answer.equals("a")) {
testerScore++;
System.out.print("Correct!");
}
else {
testerWrong++;
System.out.println("Incorrect! ");
}
System.out.println(" You hve answered " + testerScore +
" correct and " + testerWrong + " incorrect!");
}
}
This works for me. Compare your code against this and see what you are doing differently.
If you cannot find the problem that way, run your code in a debugger. Step through the program to see what it does when.
You may also want to follow Java naming conventions (variables start with lower case letters, classes start with upper case letters but aren't all upper case), to make it easier for others to read your code.

Basic Java program tune up assistance

My program asks the user for their name, then asks for a number of shuffles of 3 random numbers.
When one of the shuffles adds to the desired number (which is 31) the shuffle stops. I need to happen that the program only reads the LAST SHUFFLE. E.g.
how many shuffles do you want: 3
10 + 11 + 10 = 31 congrats you are the winner!!
The current output is:
9 + 6 + 8
8 + 10 + 12
7 + 9 + 11
I need assistance in making sure the user cannot put non alphabetical characters in their name. I also need the ability to be able to print out how many shuffles the user had before the numbers were printed out.
Here is my code,
`import java.util.InputMismatchException;
import java.util.Scanner;
import java.io.IOException;
import java.util.Random;
public class StringVariables {
public static void main(String[] args) throws NumberFormatException,
IOException {
// user inputs their name in this section
Scanner user_input = new Scanner(System.in);
//enter their first name
String first_name;
System.out.print("Enter Your First Name: ");
first_name = user_input.next();
//enter their last name
String last_name;
System.out.print("Enter Your Last Name: ");
last_name = user_input.next();
//full name printed together
String full_name;
full_name = first_name + " " + last_name;
System.out.println(full_name + " Is Now Playing");
// this is the shuffle portion as well as something to see if a number
int numShuffles = -1;
while (numShuffles < 0) {
System.out.println("How many times do you want the numbers shuffled? ");
try {
numShuffles = user_input.nextInt();
} catch (InputMismatchException inputException) {
System.out.print("Please enter a valid number. \n");
//this is the buffer that resets if the user types a letter instead of a number, or any other character
user_input.next();
}
}
// here is going to be the loop for shuffles
// we are now going to generate their random number and add a delay
// after completing their name fields
delay(3000);
System.out
.println(" You will be given a hand of 3 random numbers between 7-13"
+ "\n you will be drawn a the number of shuffles as you entered above ");
delay(2000);
System.out
.println(" Then, the computer will add the random numbers and if it is equal to 31, you win.");
/*
* end of explanation of the game, next i will create a new screen with
* the user's name and numbers
*/
delay(4000);
// printing 25 blank lines
for (int i = 0; i < 25; i++)
System.out.println(" ");
System.out.println("User playing: " + full_name);
System.out.println("Your lucky numbers are...");
// random number generator
Random random = new Random();
while (true) {
// the shuffle loop
boolean isWinner = false;
for (int i = 0; i < numShuffles; i++) {
int num1 = 7 + random.nextInt(7);
int num2 = 7 + random.nextInt(7);
int num3 = 7 + random.nextInt(7);
System.out.println(num1 + " + " + num2 + " + " + num3 + " = "
+ (num1 + num2 + num3));
// adding the numbers together
if (num1 + num2 + num3 == 31) {
isWinner = true;
System.out
.println("Congratulations !! You are the Lucky Winner !!!!");
break;
//if you loose every shuffle
}
}
if (!isWinner)
System.out.println("Better Luck Next Time");
// play again prompt
System.out
.println(" Do you want to play again? (If you do enter y or yes) \n To exit press any other key ");
String input = user_input.next();
if (!"y".equalsIgnoreCase(input) && !"yes".equalsIgnoreCase(input)) {
break;
}
}
// if pressed y or yes the program will run again with the same number of shuffles entered from before
user_input.close();
}
// delay field
public static void delay(int millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException exp) {
// delay field
}
}
}`

Arraylist numberStore = new Arraylist();
for (int i = 0; i < numShuffles; i++) {
int num1 = 7 + random.nextInt(7);
int num2 = 7 + random.nextInt(7);
int num3 = 7 + random.nextInt(7);
System.out.println(num1 + " + " + num2 + " + " + num3 + " = " + (num1 + num2 + num3));
numberStore.add(num1 + num2 + num3);
}
int lastNumber = (numberStore.size() - 1);
if (lastNumber == 31) {
isWinner = true;
System.out
.println("Congratulations !! You are the Lucky Winner !!!!");
break;
//if you loose every shuffle
}
to make sure that only the last shuffle can get read as a winner or loser.
Because you are initializing your num1, num 2... variables inside of your for loop then those variables are scoped to that for loop. I would suggest that if you want to make sure that only one set of numbers can be judged then you move the scope out of the loop. Adding the totals to an array would then allow you to choose as many as you want to judge.
When it comes to sterilizing your inputs you can use util.Scanner to do most of it for you with a little knowledge of regex:
while (!scan.hasNext("[A-Za-z]+")) {
System.out.println("Nope, that's not it!");
sc.next();
}
This will stop your scanner allowing any none alphabetical char's being entered, you can read more about Regex with this tool

ArrayList If Loop not working properly: JAVA

I have a program that asks the user their name etc. Then it asks how many times do you want the numbers to loop (so my program generates 3 random numbers between 7 and 13 and if it adds up to 31 they are the winner) and my issue is that I only want the last printed number to count towards if the player wins or looses, the other numbers are just for show or tease i guess. the problem is that regardless towards if the player wins or looses, the losing statement always prints out. Below is my entire code.
import java.util.InputMismatchException;
import java.util.Scanner;
import java.io.IOException;
import java.util.Random;
public class StringVariables {
public static void main(String[] args) throws NumberFormatException,
IOException {
// user inputs their name in this section
Scanner user_input = new Scanner(System.in);
//enter their first name
String first_name;
System.out.print("Enter Your First Name: ");
while
(!user_input.hasNext("[A-Za-z]+")) {
System.out.println("Please only enter alphabet characters. Try again.");
user_input.next();
}
first_name = user_input.next();
//enter their last name
String last_name;
System.out.print("Enter Your Last Name: ");
while
(!user_input.hasNext("[A-Za-z]+")) {
System.out.println("Please only enter alphabet characters. Try again.");
user_input.next();
}
last_name = user_input.next();
//full name printed together
String full_name;
full_name = first_name + " " + last_name;
System.out.println(full_name + " Is Now Playing");
// this is the shuffle portion as well as something to see if a number
int numShuffles = -1;
while (numShuffles < 0) {
System.out.println("How many times do you want the numbers shuffled? ");
try {
numShuffles = user_input.nextInt();
} catch (InputMismatchException inputException) {
System.out.print("Please enter a valid number. \n");
//this is the buffer that resets if the user types a letter instead of a number, or any other character
user_input.next();
}
}
// here is going to be the loop for shuffles
// we are now going to generate their random number and add a delay
// after completing their name fields
delay(3000);
System.out
.println(" You will be given " + numShuffles + " hand(s) of 3 random numbers between 7-13" );
delay(2000);
System.out
.println(" Then, the computer will add the random numbers and if it is equal to 31, you win!");
/*
* end of explanation of the game, next i will create a new screen with
* the user's name and numbers
*/
delay(4000);
// printing 25 blank lines
for (int i = 0; i < 25; i++)
System.out.println(" ");
System.out.println("User playing: " + full_name);
System.out.println("Number of times shuffled: " + numShuffles);
System.out.println("Your lucky numbers are...");
// random number generator
Random random = new Random();
while (true) {
// the shuffle loop
Arraylist numberStore = new Arraylist();
boolean isWinner = false;
for (int i = 0; i < numShuffles; i++) {
int num1 = 7 + random.nextInt(7);
int num2 = 7 + random.nextInt(7);
int num3 = 7 + random.nextInt(7);
System.out.println(num1 + " + " + num2 + " + " + num3 + " = " + (num1 + num2 + num3));
numberStore.add(num1 + num2 + num3);
int lastNumber = (numberStore.size() - 1);
if (lastNumber == 31) {
isWinner = true;
System.out.println("Congratulations !! You are the Lucky Winner !!!!");
break;
//if you loose every shuffle
}
}
if (!isWinner) {
System.out.println("Better Luck Next Time");
}
// play again prompt
System.out
.println(" Do you want to play again? (If you do enter y or yes) \n To exit press any other key ");
String input = user_input.next();
if (!"y".equalsIgnoreCase(input) && !"yes".equalsIgnoreCase(input)) {
break;
}
}
// if pressed y or yes the program will run again with the same number of shuffles entered from before
user_input.close();
}
// delay field
public static void delay(int millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException exp) {
// delay field
}
}
}

int lastNumber = (numberStore.size() - 1);
if (lastNumber == 31) {
you probably want something like
int lastNumber = numberStore.get(numberStore.size() - 1);
if (lastNumber == 31) {
to verify that is the error try to change that line to
int lastNumber = num1 + num2 + num3;
Edit based on further messages:
Looks like what you really want is this:
for (int i = 0; i < numShuffles; i++) {
int num1 = 7 + random.nextInt(7);
int num2 = 7 + random.nextInt(7);
int num3 = 7 + random.nextInt(7);
System.out.println(num1 + " + " + num2 + " + " + num3 + " = " + (num1 + num2 + num3));
numberStore.add(num1 + num2 + num3);
int lastNumber = num1 + num2 + num3;
boolean lastShuffle = (i == (numShuffles - 1));
if (lastShuffle) {
if (lastNumber == 31) {
System.out.println("Congratulations !! You are the Lucky Winner !!!!");
} else {
System.out.println("Better Luck Next Time");
}
}
}
// play again prompt
System.out
.println(" Do you want to play again? (If you do enter y or yes) \n To exit press any other key ");
String input = user_input.next();
if (!"y".equalsIgnoreCase(input) && !"yes".equalsIgnoreCase(input)) {
break;
}
Just a general suggestion: avoid to use break if possible, it makes control flow hard to follow and is not a good programming practice.

Several points to make here. One, your code is quite messy and hard to read. It's helpful when you're asking for help (and in general anyway) to properly indent your code. This is good practice and if you do other languages like Python can help you out a lot. Also, why do a check for !isWinner? Scrap the isWinner variable altogether and just check for the number equalling 31 and then have an else statement for the losing statement. Like this:
if (lastNumber == 31) {
System.out.println("Congratulations !! You are the Lucky Winner !!!!");
break;
//if you loose every shuffle
}
else {
System.out.println("Better Luck Next Time");
}
Also, take some steps to find the error. Print out each number as you get it, and use
int lastNumber = num1 + num2 + num3;
instead of
int lastNumber = (numberStore.size() - 1);
Also for anybody else compiling this, it's ArrayList and not Arraylist... just a little slip.

Sorry, I may have to say that your codes are a kind of mess up. a small factory with the solution you ask, hope it can be a little help to you
public static void main(String[] args) throws NumberFormatException,
IOException {
Scanner user_input = new Scanner(System.in);
String full_name = registeGamePlayer(user_input);
int numShuffles = initGame(user_input);
showTheGameInfo(full_name, numShuffles);
runningGame(user_input, numShuffles);
user_input.close();
}
/**
* #param user_input
* #param numShuffles
*/
private static void runningGame(Scanner user_input, int numShuffles) {
// random number generator
Random random = new Random();
while (true) {
// the shuffle loop
boolean isWinner = false;
for (int i = 0; i < numShuffles; i++) {
int num1 = 7 + random.nextInt(7);
int num2 = 7 + random.nextInt(7);
int num3 = 7 + random.nextInt(7);
int amount = num1 + num2 + num3;
System.out.printf("%d + %d + %d = %d \n", num1,num2,num3,amount);
if (amount == 31) {
isWinner = true;
System.out.println("Congratulations !! You are the Lucky Winner !!!!");
break;
// if you loose every shuffle
}
}
if (!isWinner) {
System.out.println("Better Luck Next Time");
}
// play again prompt
System.out.println(" Do you want to play again? (If you do enter y or yes) \n To exit press any other key ");
String input = user_input.next();
if (!"y".equalsIgnoreCase(input) && !"yes".equalsIgnoreCase(input)) {
break;
}
}
}
/**
* #param full_name
* #param numShuffles
*/
private static void showTheGameInfo(String full_name, int numShuffles) {
// printing 25 blank lines
for (int i = 0; i < 25; i++)
System.out.println(" ");
System.out.println("User playing: " + full_name);
System.out.println("Number of times shuffled: " + numShuffles);
System.out.println("Your lucky numbers are...");
}
// delay field
public static void delay(int millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException exp) {
// delay field
}
}
private static String registeGamePlayer(Scanner user_input){
String first_name;
System.out.print("Enter Your First Name: ");
while (!user_input.hasNext("[A-Za-z]+")) {
System.out
.println("Please only enter alphabet characters. Try again.");
user_input.next();
}
first_name = user_input.next();
// enter their last name
String last_name;
System.out.print("Enter Your Last Name: ");
while (!user_input.hasNext("[A-Za-z]+")) {
System.out
.println("Please only enter alphabet characters. Try again.");
user_input.next();
}
last_name = user_input.next();
// full name printed together
String full_name;
full_name = first_name + " " + last_name;
System.out.println(full_name + " Is Now Playing");
return full_name;
}
private static int initGame(Scanner user_input){
// this is the shuffle portion as well as something to see if a number
int numShuffles = -1;
while (numShuffles < 0) {
System.out.println("How many times do you want the numbers shuffled? ");
try {
numShuffles = user_input.nextInt();
} catch (InputMismatchException inputException) {
System.out.print("Please enter a valid number. \n");
// this is the buffer that resets if the user types a letter
// instead of a number, or any other character
user_input.next();
}
}
// here is going to be the loop for shuffles
// we are now going to generate their random number and add a delay
// after completing their name fields
delay(3000);
System.out.println(" You will be given " + numShuffles + " hand(s) of 3 random numbers between 7-13");
delay(2000);
System.out.println(" Then, the computer will add the random numbers and if it is equal to 31, you win!");
/*
* end of explanation of the game, next i will create a new screen with
* the user's name and numbers
*/
delay(4000);
return numShuffles;
}

How to randomly position a variable within X + Y = Z operation and loop

I basically want to be able to loop an X + Y = Z equation until the user inputs something other than an integer, like the letter "A" and also when having any number make the loop stop displaying a message.
Also, I am confused on how to randomly position the "?" which the user must input the correct answer.
For example
System.out.println("What is: " + num1 + " + ? = " + answer);
So far:
I am positioning the "?" manually through the IF statements. Can this be done in a more efficient way?
public static void main(String[] args) {
Random rand = new Random();
Scanner input = new Scanner(System.in);
int num1, num2, number3, answer;
do {
num1= 1 + rand.nextInt(10);
num2= 1 + rand.nextInt(10);
answer= num1 + num2;
System.out.println("What is: " + num1 + " + ? = " + answer);
number3= input.nextInt();
if (number3 == num2)
System.out.println("That is correct");
else
System.out.println("That is wrong");
num1= 1 + rand.nextInt(10);
num2= 1 + rand.nextInt(10);
answer= num1 + num2;
System.out.println(num1 + " + ? = " + answer);
number3= input.nextInt();
} while(number3 !=0);
}

Here is one way to do it:
public static void main(String[] args) {
Random rand = new Random();
Scanner scanner = new Scanner(System.in);
int[] xyz = new int[3];
String[] display = new String[3];
int answer, position;
do {
xyz[0] = 1 + rand.nextInt(10);
xyz[1] = 1 + rand.nextInt(10);
xyz[2] = xyz[0] + xyz[1];
for (int i = 0; i < xyz.length; i++)
display[i] = String.valueOf(xyz[i]);
position = rand.nextInt(3);
display[position] = "?";
System.out.println("What is: " + display[0] + " + " + display[1] + " = " + display[2]);
do {
System.out.println("Please enter an integer or 'S' to stop");
String input = scanner.nextLine();
if (input.equals("S")) {
scanner.close();
System.out.println("Stopped");
return;
}
else if (input.matches("\\d+")) { // \\d+ means "a digit (0-9) once or more
answer = Integer.parseInt(input);
break;
}
} while (true);
if (answer == xyz[position])
System.out.println("That is correct");
else
System.out.println("That is wrong");
} while (true);
}
Notes:
I use an inner do-while loop to repeatedly check the input and ask the user for a valid input.
I use 2 arrays: one for storing the numbers and another for storing the display values.
I also added a stop condition since the outer loop is infinite. Always close the Scanner when you finish.
I randomly pick 1 of 3 positions for the "?".