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Java lottery program, having trouble comparing outputs

I have to do an 'instant lottery' program in my first computer science class. All semester my professor has read verbatim from the book, so now I am a little lost, truthfully. I know how to do most of it, but am just having trouble figuring out array sort and how to compare user input and the random number output. My professor refuses to answer questions about take home assignments and has banned the use of anything except: arrays, loops and math.random- so no sets or anything more complex that could help. I've seen other programs that compile, but all with sets.
I have the code for user input of the lottery numbers and to generate the output of the random numbers. I can most likely also figure out how to print the payout with if/else. I just need to know how to get the program to compare the numbers an figure out if the user is a "winner" or not.
import java.util.Scanner;
public class TheLottery {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in); //user input of their lottery numbers
System.out.print("Enter number 1: ");
int num1 = keyboard.nextInt();
System.out.print("Enter number 2: ");
int num2 = keyboard.nextInt();
System.out.print("Enter number 3: ");
int num3 = keyboard.nextInt();
System.out.print("Enter number 4: ");
int num4 = keyboard.nextInt();
System.out.print("Enter number 5: ");
int num5 = keyboard.nextInt();
System.out.print("Enter number 6: ");
int num6 = keyboard.nextInt();
}
int[] lottery = new int[6];
int randomNum;
{
for (int i = 0; i < 6; i++) {
randomNum = (int) (Math.random() * 50); // Random number created here.
for (int x = 0; x < i; x++) {
if (lottery[x] == randomNum) // Here, code checks if same random number generated before.
{
randomNum = (int) (Math.random() * 50);// If random number is same, another number generated.
x = -1; // restart the loop
}
}
lottery[i] = randomNum;
}
for (int i = 0; i < lottery.length; i++)
System.out.print(lottery[i] + " "); //print random numbers
}
}
the final program should have the user enter 6 numbers, the program compare the numbers for matches, figure out if the user is a 'winner', show the prize and an added thing is show how much they spent (each 'ticket' is $1) vs how much they won. So far all that outputs is the scanner and random numbers

It looks like you obtained six numbers then didn't use them. Your lottery array is automatically initialized to zero. I think you're trying to compare an array with inputs to a random array, so you need a loop to put your entered values into. After you do that, initialize your random array, then just compare the arrays.
public static void main(System[] args) {
Scanner in = new Scanner(System.in);
int[] lottery = new int[6];
System.out.println("Enter " + lottery.length + " numbers: ");
for (int i = 0; i < lottery.length; i++) {
lottery[i] = in.nextInt();
}

The specific question has to do with how to do the comparison and figuring a "winner". It isn't clear what makes the definition of "winner".
Based upon my comment, and as shown in the answer by #szoore, I would use an array to collect the input. I'd use a method to collect (since one can change to use a different method for the selections, which makes testing easier).
/**
* Obtain the specified number of entries from the user
*/
public static int[] getUserSelections(final int numSelections)
{
Scanner in = new Scanner(System.in);
// read N entries from the user
int[] nums = new int[numSelections];
// NOTE: no error processing in this loop; should be refined
// bad numbers (e.g., negative, too large), duplicate entries, etc.
// need to be removed
for (int i = 0; i < numSelections; ++i) {
System.out.print("Enter number " + (i + 1) + ": ");
nums[i] = in.nextInt();
}
return nums;
}
The OP has a basic generation for the lottery numbers, but again I'd use a method. This has a slight refinement to the duplicate check, by using a method, and also allows the same duplicate check method to be later used for checking matches:
public static int[] getLotteryNumbers(final int numSelections)
{
// the largest number to be selected; all numbers between
// 1 and maxNum (inclusive) will have equal(-ish) probability
// of being generated
final int maxNum = 50;
int[] lottery = new int[numSelections];
Random rnd = new Random();
// make N random selections, and ensure we don't have duplicates
for (int i = 0; i < numSelections; ++i) {
boolean generate = true;
while (generate) {
int sel = rnd.nextInt(maxNum) + 1;
generate = numberInArray(sel, lottery);
if (! generate) {
lottery[i] = sel;
}
}
}
return lottery;
}
/**
* Returns true if the specific queryNum is found in the pastSelections
* Could be slightly optimized by passing how many selections have
* already been made
*/
public static boolean numberInArray(int queryNum, int[] pastSelections)
{
// look at each element and see if already there; exit via return
// if so
for (int i = 0; i < pastSelections.length; ++i) {
if (pastSelections[i] == queryNum) {
return true;
}
}
return false;
}
The use of the method 'numberInArray' then allows for fairly easy check on how many numbers match:
// see how many match
int matches = 0;
// see if the user entry exists in the lottery; if so, we
// have a match
for (int i = 0; i < userEntries.length; ++i) {
if (numberInArray(userEntries[i], lottery)) {
++matches;
}
}
System.out.printf("Found %2d matches%n", matches);
Determining payouts, etc. is straight forwarding using if/else or (perhaps better) a switch based on the number of matches.
Also, the entries and lottery selections should probably be sorted. It isn't clear if the built-in sort may be used or not. Write the sort method as appropriate:
/**
* Sorts the array; implement sorting as needed
*/
public static void sort(int[] arr)
{
Arrays.sort(arr);
}
/*
* outputs the array if one cannot use Arrays.toString(arr)
*/
public static void outputArray(int[] arr)
{
for (int i = 0; i < arr.length; ++i) {
System.out.printf("%2d ", arr[i]);
}
System.out.println();
}
Sample main:
public static void main(String[] args)
{
// how many options for the lottery; here it is 6
final int numEntries = 6;
// this method obtains from user
int[] userEntries;
userEntries = getUserSelections(numEntries);
sort(userEntries);
// display User selections
outputArray(userEntries);
int[] lottery = getLotteryNumbers(numEntries);
sort(lottery);
// display lottery numbers
outputArray(lottery);
// see how many match
int matches = 0;
// see if the user entry exists in the lottery; if so, we
// have a match
for (int i = 0; i < userEntries.length; ++i) {
if (numberInArray(userEntries[i], lottery)) {
++matches;
}
}
System.out.printf("Found %2d matches%n", matches);
//
// TODO: calculate winnings based upon the number of matches
//
}

The loop runs twice in a single run

This problem is from https://www.hackerrank.com/ and link to it is https://www.hackerrank.com/challenges/java-list/problem .
In the below code while loop is running twice as according to question we need to enter Q, Q times an operation to perform in the Array Declared. For this, i am running twice the loop so that I can get the desired result.
import java.util.*;
public class javaList {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int N = sc.nextInt();
int i, x;
ArrayList L = new ArrayList(N);
for (i = 0; i < N; i++) {
L.add(sc.nextInt());
}
int Q = sc.nextInt();
i = 0;
// for normal running i have multiplied Q by 2 so that i can get the results
while (i < Q * 2) {
System.out.println("Loop: " + i);
String s = sc.nextLine();
int sz = L.size();
// code for checking insert
if (s.equals("Insert")) {
x = sc.nextInt();
int y = sc.nextInt();
//if the position i am looking exists then just replace
// i need to insert at index x of array L but array.size() gives one more than the last index
if ((sz - 1) >= x) {
L.add(x, y);
}
//if the position i am looking does not exist then create
else {
for (int j = sz; j <= x; j++) {
//add number to desired place
if (j == x)
L.add(y);
//in between the two endings of array and insertion adding default value 0
else
L.add(0);
}
}
//checking code for Delete
} else if (s.equals("Delete")) {
x = sc.nextInt();
//if the desired location exists then only replace
if ((sz - 1) >= x) {
L.remove(x);
}
}
i++;
}
for (i = 0; i < L.size(); i++) {
System.out.print(L.get(i) + " ");
}
}
}
I want to Know why the loop is running twice in a single run.

So, from discussion in the comments, you've stated that your question is:
if Q = 2 then it should ask operations Insert or Delete 4 times as of my code. But it asks only 2 times. Simply that is my problem
First, you may not fully understand your own program flow. Before the while loop, you need to enter three sets of values, a value for N, values for L, and a value for Q.
Once you enter your while loop, you will be prompted for a value for s (which it seems you intend to be either "Insert" or "Delete"). However, the first time around, it will get an empty string and s will be "\n". Why? Because for N, L, and Q, the user will enter values as follows:
[value] [ENTER]
The return key is itself a value. So, in the input buffer (assuming Q = 2), is "2\n". When your code runs to get s String s = sc.nextLine(); it will see the next line symbol and skip prompting user for input.
Because s is not "Insert" or "Delete", it will skip those the first time around. You will then be prompted to enter a value for "s" after the start next loop.
To help you realize what's going on, I suggest adding statements everywhere you ask users to enter a value, like System.out.println("Enter a value for Q:");
This will help you keep track of program flow.

Your code is waaay to complicated. Try this:
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
List<Integer> list = new ArrayList<>();
for (int i = 0, n = scanner.nextInt(); i < n; i++) {
list.add(scanner.nextInt());
}
for (int i = 0, n = scanner.nextInt(); i < n; i++) {
if (scanner.next().equals("Insert")) {
list.add(scanner.nextInt(), scanner.nextInt());
} else {
list.remove(scanner.nextInt());
}
}
String result = list.stream()
.map(String::valueOf)
.collect(Collectors.joining(" "));
System.out.println(result);
}

How to add even numbers in a range using a for loop

I have to create a program that gets a range from the user then adds each even number in the range and prints to screen. I am struggling to figure out how to add each number in the for loop. If the range is 5 to 10 the screen should print 24 as the answer. Below is my code.
//worksheet 4 - question 3
//asks user for a range. Adds even numbers in range and prints their sum.
import java.util.Scanner;
class P3LoopRange
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int initial, finalValue;
System.out.print("Enter a start value: ");
initial = input.nextInt();
System.out.print("Enter a second value: ");
finalValue = input.nextInt();
while (finalValue <= initial)
{
System.out.println("Second value must be larger than start value.");
System.out.print("Enter a second value: ");
finalValue = input.nextInt();
}
int range = finalValue - initial;
int x = 0
for (int i = initial; i <= finalValue; i++)
{
if (i%2==0)
{
int x = x+i;
}
}
System.out.printf(x);
}
}

You declare twice the x local variable.
You cannot as it is not legal to have a duplicate local variable.
Besides, declaring it inside the loop makes it be overwritten at each iteration.
So, just declare it before the loop and it should be fine.
int x = 0;
for (int i = initial; i <= finalValue; i++)
{
if (i%2 == 0)
{
x = x + i;
}
}

Change int x = x+i; to x=x+i;. Here you are re initializing x each time.

Problem is at: int x = x+i;
just remove int and your problem is solved

Moving Average Using User-Input Array

I need to write a program that calculates a moving average by a user inputted array. The first element of the array is the window size, and the input is terminated by a 0. The output values are printed with two digits after the decimal point.
Example input: 3 2 4 7 7 8 11 12 0
Corresponding Output: 4.33 6.00 7.33 8.67 10.33
(4.33 is average of 2,4,7 and 6 is average of 4,7,7 etc.)
Here's my code so far:
package movingaverage;
import java.util.Scanner;
public class MovingAverage {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int[] arr = new int[n];
int sum = 0;
for (int i = 0; i < n; i++) {
sum += arr[i];
}
avg[0] = sum / 5;
int j = 1;
for (int i = 5; i < arr.length; i++) {
sum = sum + arr[i] - arr[i - 5];
avg[j++] = sum / 5;
}
}
}
I think I have the loop right, but I'm not sure how to get the array to end at 0.

This is a possible solution.
public class Test
{
private static final Scanner SCANNER;
static {
SCANNER = new Scanner(System.in);
}
public static final void main(final String... args) {
final String[] numbers = SCANNER.nextLine().trim().split(" ");
final int consideredElements = Integer.parseInt(numbers[0]);
float sum = 0;
int value = 0;
for (int i = 1; i < numbers.length; i++) {
sum = 0;
for (int k = 0; k < consideredElements; k++) {
value = Integer.parseInt(numbers[i + k]);
if (value == 0) {
return;
}
sum += value;
}
System.out.println(new BigDecimal(sum / consideredElements).setScale(2, RoundingMode.HALF_EVEN));
}
}
}

First, you are using 5 in a couple of places in your program, I see no justification for that. Could it be that your expectation of user input lead you to put 5 where the number you really should use, depends on user input? Maybe you should use the window size instead? I’m guessing a bit here.
Next, as #lppEdd pointed out, you are not reading the numbers from your input — only the window size.
Next, you are declaring your array of size n, which I believe was your window size, not your array size. I believe the real solution to this problem is using better and more explanatory variable names.
Your code does not compile since you have not declared the array avg that you try to store your moving average into.
Fifth, when you want your average as a double, you need to convert to double before dividing (this is a classic pitfall that has already generated many questions on Stack Overflow).
I hope this gets you a couple of steps further.

Java Random Utility Generating Too Many 0's And Static Numbers

The line birthdays[j] = rnd.nextInt(365); seems to generate extra 0's in the int[] birthdays array. It also seems to add an EXTRA 0 into the array and generate static values depending on how many simulations I run and how many birthdays I generate. For instance, if I do 5 simulations and enter a 3 for the number of people in each simulation's "birthday pool" I always get an array of [0, 0, 289, 362].
Any help understanding the problem would be greatly appreciated.
public static void main(String[] args) {
System.out.println("Welcome to the birthday problem Simulator\n");
String userAnswer="";
Scanner stdIn = new Scanner(System.in);
do {
int [] userInput = promptAndRead(stdIn);
double probability = compute(userInput[0], userInput[1]);
// Print results
System.out.println("For a group of " + userInput[1] + " people, the probability");
System.out.print("that two people have the same birthday is\n");
System.out.println(probability);
System.out.print("\nDo you want to run another set of simulations(y/n)? :");
//eat or skip empty line
stdIn.nextLine();
userAnswer = stdIn.nextLine();
} while (userAnswer.equals("y"));
System.out.println("Goodbye!");
stdIn.close();
}
// Prompt user to provide the number of simulations and number of people and return them as an array
public static int[] promptAndRead(Scanner stdIn) {
int numberOfSimulations = 0;
while(numberOfSimulations < 1 || numberOfSimulations > 50000) {
System.out.println("Please Enter the number of simulations to do. (1 - 50000) ");
numberOfSimulations = stdIn.nextInt();
}
int sizeOfGroup = 0;
while(sizeOfGroup < 2 || sizeOfGroup > 365) {
System.out.println("Please Enter the size of the group of people. (2 - 365) ");
sizeOfGroup = stdIn.nextInt();
}
int[] simulationVariables = {numberOfSimulations, sizeOfGroup};
return simulationVariables;
}
// This is the method that actually does the calculations.
public static double compute(int numOfSims, int numOfPeeps) {
double numberOfSims = 0.0;
double simsWithCollisions = 0.0;
int matchingBirthdays = 0;
int[] birthdays = new int[numOfPeeps + 1];
int randomSeed = 0;
for(int i = 0; i < numOfSims; i++)
{
randomSeed++;
Random rnd = new Random(randomSeed);
birthdays = new int[numOfPeeps + 1];
matchingBirthdays = 0;
for(int j = 0; j < numOfPeeps; j++) {
birthdays[j] = rnd.nextInt(365);
Arrays.sort(birthdays);
}
for(int k = 0; k < numOfPeeps; k++) {
if(birthdays[k] == birthdays[k+1]) {
matchingBirthdays++;
}
}
if(matchingBirthdays > 0) {
simsWithCollisions = simsWithCollisions + 1;
}
}
numberOfSims = numOfSims;
double chance = (simsWithCollisions / numberOfSims);
return chance;
}
}

The line "birthdays[j] = rnd.nextInt(365);" seems to generate extra 0's in the int[] birthdays array.
Well, it doesn't. The array elements where zero to start with.
What that statement actually does is to generate a single random number (from 0 to 364) and assign it to one element of the array; i.e. the jth element. That is not what is required for your problem.
Now, we could fix your code for you, but that defeats the purpose of your homework. Instead I will give you a HINT:
The birthdays array is supposed to contain a COUNT of the number of people with a birthday on each day of the year. You have to COUNT them. One at a time.
Think about it ...

int arrays are by default initialized to 0 unless explicitly specified. Please see this Oracle tutorial about Arrays.

I found the problem myself. The issue was that having the "Arrays.sort(birthdays);" statement inside of a loop. That generated extra 0's.