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Issue with flow of a program

I am new to Java and just learning the basics.
I have gone through if checks/statements(if-if-if; if-else if-else, if-else), while and for loops as well. I have an assignment which I can not for the life of me figure out. I am having some issues with the flow of the program itself and I just get it to work half way through in Eclipse.
The idea of the program is for it to accept three integers from the keyboard(keyboard input using Scanner) and print out all numbers, between 0 and the first integer from the input, which can be divided by the second and third input integers, respectively. The first input integer has to be between 200 and 100. I will provide what code I have written. I can get the program to accept input but then I get the message in the console.
I set up the three integers, I set up a condition for the first integer using a while loop and then I use a for loop to print all the numbers between 0 and the first input integer. Then within the for loop I do in if check and print out all the numbers. It accepts the input three times but then I just goes to terminated status.
package Javawork;
import java.util.Scanner;
public class Test {
private static Scanner keyboard;
public static void main(String[] args) {
firstProgramme();
}
public static void firstProgramme() {
keyboard = new Scanner(System.in);
System.out.println("Enter number: ");
int firstNum = keyboard.nextInt();
int secondNum = keyboard.nextInt();
int thirdNum = keyboard.nextInt();
while (firstNum > 100 && firstNum < 200) {
for (int i = 0; i <= firstNum; i++) {
if (i % secondNum == 0 && i % thirdNum == 0) {
System.out.println(i);
}
}
}
}
}

As per your requirement you need to check whether the first number is between 100 and 200. For that you should use
if(firstNum > 100 && firstNum < 200) {
instead of
while(firstNum > 100 && firstNum < 200) {
As if will check the condition and while will iterate based on condition.

Processing numbers program

Firstly, I'm taking AP Computer Science this year, and this question is related to an exercise we were assigned in class. I have written the code, and verified that it meets the requirements to my knowledge, so this is not a topic searching for homework answers.
What I'm looking for is to see if there's a much simpler way to do this, or if there's anything I could improve on in writing my code. Any tips would be greatly appreciated, specific questions asked below the code.
The exercise is as follows: Write a program called ProcessingNumbers that does:
Accepts a user input as a string of numbers
Prints the smallest and largest of all the numbers supplied by the user
Print the sum of all the even numbers the user typed, along with the largest even number typed.
Here is the code:
import java.util.*;
public class ProcessingNumbers {
public static void main(String[] args) {
// Initialize variables and objects
Scanner sc = new Scanner(System.in);
ArrayList<Integer> al = new ArrayList();
int sumOfEven = 0;
// Initial input
System.out.print("Please input 10 integers, separated by spaces.");
// Stores 10 values from the scanner in the ArrayList
for(int i = 0; i < 10; i++) {
al.add(sc.nextInt());
}
// Sorts in ascending order
Collections.sort(al);
// Smallest and largest values section
int smallest = al.get(0);
int largest = al.get(al.size() - 1);
System.out.println("Your smallest value is " + smallest + " and your largest value is " + largest);
// Sum of Even numbers
int arrayLength = al.size();
for (int i = 0; i < al.size(); i++) {
if (al.get(i) % 2 == 0) {
sumOfEven += al.get(i);
}
}
System.out.println("The sum of all even numbers is " + sumOfEven);
// Last section, greatest even number
if (al.get(arrayLength - 1) % 2 == 0) {
System.out.println("The greatest even number typed is " + al.get(arrayLength - 1));
} else {
System.out.println("The greatest even number typed is " + al.get(arrayLength - 2));
}
sc.close();
}
}
Here are specific questions I'd like answered, if possible:
Did I overthink this? Was there a much simpler, more streamlined way to solve the problem?
Was the use of an ArrayList mostly necessary? We haven't learned about them yet, I did get approval from my teacher to use them though.
How could I possibly code it so that there is no 10 integer limit?
This is my first time on Stackoverflow in quite some time, so let me know if anything's out of order.
Any advice is appreciated. Thanks!

Usage of the ArrayList wasn't necessary, however it does make it much simpler due to Collections.sort().
To remove the 10 integer limit you can ask the user how many numbers they want to enter:
int numbersToEnter = sc.nextInt();
for(int i = 0; i < numbersToEnter; i++) {
al.add(sc.nextInt());
}
Another note is that your last if-else to get the highest even integer doesn't work, you want to use a for loop, something like this:
for (int i = al.size() - 1; i >= 0; i--) {
if (al.get(i) % 2 == 0) {
System.out.println("The greatest even number typed is " + al.get(i));
break;
}

I wouldn't say so. Your code is pretty straightforward and simple. You could break it up into separate methods to make it cleaner and more organized, though that isn't necessary unless you have sections of code that have to be run repeatedly or if you have long sections of code cluttering up your main method. You also could have just used al.size() instead of creating arrayLength.
It wasn't entirely necessary, though it is convenient. Now, regarding your next question, you definitely do want to use an ArrayList rather than a regular array if you want it to have a variable size, since arrays are created with a fixed size which can't be changed.
Here's an example:
int number;
System.out.print("Please input some integers, separated by spaces, followed by -1.");
number = sc.nextInt();
while (number != -1) {
al.add(number);
number = sc.nextInt();
}

Here is a solution that:
Doesn't use Scanner (it's a heavyweight when all you need is a line of text)
Doesn't have a strict limit to the number of numbers
Doesn't need to ask how many numbers
Doesn't waste space/time on a List
Handles the case when no numbers are entered
Handles the case when no even numbers are entered
Fails with NumberFormatException if non-integer is entered
Moved actual logic to separate method, so it can be mass tested
public static void main(String[] args) throws Exception {
System.out.println("Enter numbers, separated by spaces:");
processNumbers(new BufferedReader(new InputStreamReader(System.in)).readLine());
}
public static void processNumbers(String numbers) {
int min = 0, max = 0, sumOfEven = 0, maxEven = 1, count = 0;
if (! numbers.trim().isEmpty())
for (String value : numbers.trim().split("\\s+")) {
int number = Integer.parseInt(value);
if (count++ == 0)
min = max = number;
else if (number < min)
min = number;
else if (number > max)
max = number;
if ((number & 1) == 0) {
sumOfEven += number;
if (maxEven == 1 || number > maxEven)
maxEven = number;
}
}
if (count == 0)
System.out.println("No numbers entered");
else {
System.out.println("Smallest number: " + min);
System.out.println("Largest number: " + max);
if (maxEven == 1)
System.out.println("No even numbers entered");
else {
System.out.println("Sum of even numbers: " + sumOfEven);
System.out.println("Largest even number: " + maxEven);
}
}
}
Tests
Enter numbers, separated by spaces:
1 2 3 4 5 6 7 8 9 9
Smallest number: 1
Largest number: 9
Sum of even numbers: 20
Largest even number: 8
Enter numbers, separated by spaces:
1 3 5 7 9
Smallest number: 1
Largest number: 9
No even numbers entered
Enter numbers, separated by spaces:
-9 -8 -7 -6 -5 -4
Smallest number: -9
Largest number: -4
Sum of even numbers: -18
Largest even number: -4
Enter numbers, separated by spaces:
No numbers entered

How to close a while loop

I thought my code was correct but when I ran it, my output statements at the bottom wouldnt produce. I'm asking the keyboard to enter any number and then to end by entering -1. My while loop includes adding numbers, creating a sum, as well as giving the amount of even numbers. When I test my code I've been entering just 1,2,3,4 hoping to produce 4 total numbers. 2 even, and a sum of 10. Why isnt' my code getting to the print statements?
public static void main(String[] args) {
Scanner sc = new Scanner (System.in);
System.out.println("Please enter a number. Enter -1 to stop program.");
int num = sc.nextInt();
int counter = 0;
int even = 0;
int sum = 0;
while (num != -1)
{
counter += 1;
sum += num;
if (num%2 == 0)
{
even +=1;
}
}
System.out.println("You have entered "+ counter + "number(s)");
System.out.println("You have entered "+ even + "even numbers");
System.out.println("The sum for the numbers you entered is "+ sum);
}

You never get the input again so the loop runs infinitely. You need to get the value again.
while (num != -1)
{
...
num = sc.nextInt();
}

num gets set before you enter the loop.
So, when does the num change inside the while loop? It doesn't. That's why your code won't exit the loop.
I suggest moving the
num = sc.nextInt();
inside the loop.

java while loop won't print the text after a the stopping condition [closed]

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I just started studying Java and I'm required to use while to decided how many players can be goalkeepers based on their number. The loop is supposed to stop after the user entered 0 and print the counted number of players that can be goalkeepers.
public class Q3_201303719 {
public static void main(String[] args) {
Scanner input = new Scanner (System.in);
int num; int count=0;
System.out.println("Enter the players' numbers");
num = input.nextInt();
while ((num != 0) && (num < 31) && (num%2==0) || (num%3==0))
count++;
System.out.println(count+ " players can be goalkeepers.\n");
// Above line should be printed once the user enter 0, but in my case it won't
// print and keeps asking the user to enter a number.
}
}

From the question it is difficult to understand what it is you are trying to achieve. However, we can try to help you understand the code as it is written.
The while loop is currently written as:
while ((num != 0) && (num < 31) && (num%2==0) || (num%3==0))
This could be rewritten as the following and it would not make any difference:
while (num != 0 && num < 31 && num%2==0 || num%3==0)
The additional parenthesis that you included are not required.
In Java the operator precedence is && before ||. This means that the && operators will be evaluated first, followed by the ||. Therefore, the above statement could therefore be rewritten as the following and it would not make any difference:
while ((num != 0 && num < 31 && num%2==0) || num%3==0)
However, it may make the code a little easier to understand.
So when the code executes the following occurs:
The count variable is initialised to 0.
A value is retrieved and stored in the variable num. Lets say that this value is 10.
The while statement is evaluated for the first time:
num != 0 is true as 10 != 0.
num < 31 is true as 10 is less than 31.
num%2==0 is true as 10 divided by 2 is 5 and leaves a remainder of 0.
As these all evaluate to true, the OR part (num%3==0) is not evaluated as it is not neccessary. See short circuit evaluation (http://users.drew.edu/bburd/JavaForDummies4/ShortCircuitEval.pdf).
The count is incremented to 1.
The loop executes again for the second time. num is still 10.
num != 0 is true as 10 != 0.
num < 31 is true as 10 is less than 31.
num%2==0 is true as 10 divided by 2 is 5 and leaves a remainder of 0.
The count is incremented to 2.
And so on... in an infinite loop.
If the variable num was instead set to 9. The loop would evaluate as follows:
num != 0 is true as 9 != 0.
num < 31 is true as 9 is less than 31.
num%2==0 is false as 9 divided by 2 is 4 and leaves a remainder of 1.
Therefore, now the || part is evaluted:
num%3==0 is true as 9 divided by 3 is 3 and leaves a remainder of 0.
Again, this would result in an infinite loop.
If the variable num was instead 0:
num != 0 is false
As the first num!=0 is false, the num<31 and num%2==0 parts are not evaluated as their results would not make any difference.
The num%3==0 is then evaluated:
num%3==0 is true as 0 divided by 3 leaves a remainder of 0.
Again, this would result in an infinite loop.
I hope that this may help to clarify your understanding and allow you to correct the code appropriately.

how many players' numbers do you have to input?
you have a while loop that depends on num value, but you never change the num value. that will end up in endless loop...
if you have more players, create a for loop to enter the numbers, store the numbers in an array or an arraylist and if you use the while loop, use it so that it depends on a value that you change inside the loop. otherwise it will loop forever.
do{
System.out.println("Enter the players' numbers");
num = input.nextInt();
count++;
}while(num!=0);
your code with this should look like this:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num;
int count = 0;
do {
System.out.println("Enter the players' numbers");
num = input.nextInt();
count++;
} while (num != 0);
System.out.println(count + " players can be goalkeepers.\n");
// Above line should be printed once the user enter 0, but in my case it
// won't
// print and keeps asking the user to enter a number.
}

If you can't use a do-while-loop as Ubica suggested, then you need to work your way around it:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num=2; // you need to initialize num with a value, that allows you to go inside the while loop at least once
int count = 0;
while((num != 0) && (num < 31) && (num % 2 == 0) || (num % 3 == 0)) {
System.out.println("Enter the players' numbers");
num = input.nextInt(); // user input is here inside the loop
count++; // your count will count every valid input + the user input that ends the loop
}
count--; // if your user entered 0 to exit the loop, count would have still incremented, so you need do subtract one again
System.out.println(count + " players can be goalkeepers.\n");
}
As I commented in the code, first you initialize num with a dummy value, that allows you to enter the loop at least once. Then you listen to the users input and count the loop iterations. But since the loop will execute at least once (even though your user might enter 0 right away to exit the loop) your count would be one higher than the actual number of valid inputs. So you have to subtract that 1 from your count again.
EDIT
I forgot to mention: your loop will not stop when the user enters 0 because
(num % 3 == 0) // is true with num=0
so when the user enters 0 the while condition will evaluate like this:
while( false && true && true || true )
while( false || true )
while( true )

The bracketing for the loop should fix this problem.

You need braces surrounding your while loop block. As a general rule, it is best to overuse braces rather than under-use them.
Your code should look like:
package q3_201303719;
import java.util.Scanner;
public class Q3_201303719 {
public static void main(String[] args) {
Scanner input = new Scanner (System.in);
int num; int count=0;
System.out.println("Enter the players' numbers");
num = input.nextInt();
while((num != 0) && (num < 31)&& (num%2==0)|| (num%3==0)) {
count++;
}
// The braces added above are required for the while loop and will keep your program
// from not outputting your results.
System.out.println(count+ " players can be goalkeepers.\n");
}
}
Best of luck and happy coding. :)

Your code isn't making sense.
1st : The While loop is not modifying the "num" value, resulting in
infinite loop if entered.
2nd : What is the code supposed to do? It is really hard to tell from what you show.
I think placing while loop upper could help you, but still code makes no much sense
public class Q3_201303719 {
public static void main(String[] args) {
int num = 0; int count=0;
while((num != 0) && (num < 31)&& (num%2==0)|| (num%3==0)) {
Scanner input = new Scanner (System.in);
System.out.println("Enter the players' numbers");
num = input.nextInt();
count++;
}
System.out.println(count+ " players can be goalkeepers.\n");
// Above line should be printed once the user enter 0, but in my case it won't
// print and keeps asking the user to enter a number.
}
}
Edit :
This problem occurred because you didn't follow a really simple rule : think before coding.
For this exercise you need to think about what your code should be doing, and then write the code for it. Coding is just a language, if you know what you want to write then it is easier. Here you obviously don't really know what you wanna do, and as you are new with development it was likely that you get stucked

java program outputting even/odd numbers

My task is to write a java program that first asks the user how many numbers will be inputted, then outputs how many odd and even numbers that were entered. It is restricted to ints 0-100. My question is: What am I missing in my code?
import java.util.Scanner;
public class Clancy_Lab_06_03 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int n;
System.out.println("How many numbers will be entered?");
n = input.nextInt();
while (n < 0 || n > 100) {
System.out.println("ERROR! Valid range 0-100. RE-Enter:");
n = input.nextInt();
n++;
}
int odd = 0;
int even = 0;
while (n >= 0 || n <= 100) {
n = input.nextInt();
if (n % 2 == 0) {
even++;
} else {
odd++;
}
}
System.out.println(even + "even" + odd + "odd");
}
}

Second while loop is infinite. Relplace it with something like this:
for (int i = 0; i < n; i++) {
int b = input.nextInt();
if (b % 2 == 0) {
even++;
} else {
odd++;
}
}
Also I don't understand why are you incrementing n in first loop. For example when you will first give -5, you will be asked to re-enter the number. Then you type -1, but it gets incremented and in fact program processes 0, altough user typed -1. In my opinion it is not how it suppose to work and you should just remove this n++.
As you asked in comment - the same using while loop:
while(n > 0) {
n--;
int b = input.nextInt();
if (b % 2 == 0) {
even++;
} else {
odd++;
}
}
Also it is good idea to close input when you no longer need it (for example at the end of main method)
input.close();

You had two issues - first you were incrementing n in the first loop, rather than waiting for the user to enter a valid number.
In the second loop, you weren't comparing the number of entries the user WANTED to make with the number they HAD made - you were over-writing the former with the new number.
This version should work, although I've not tested it as I don't have java on this machine.
Note that we now sit and wait for both inputs, and use different variable names for the "how many numbers will you enter" (n) and "what is the next number you wish to enter" (num) variables? Along with a new variable i to keep track of how many numbers the user has entered.
import java.util.Scanner;
public class Clancy_Lab_06_03
{
public static void main (String[] args)
{
Scanner input = new Scanner (System.in);
int n;
System.out.println ("How many numbers will be entered?");
n = input.nextInt();
//Wait for a valid input
while (n < 0 || n > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
n = input.nextInt();
}
//Setup variables for the loop
int odd = 0;
int even = 0;
int num;
//Keep counting up until we hit n (where n is the number of entries the user just said they want to make)
for(int i = 0; i < n; i++)
{
//Changed this, because you were over-writing n (remember, n is the number of entries the user wants to make)
//Get a new input
while (num < 0 || num > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
num = input.nextInt();
}
//Check whether the user's input is even or odd
if (num % 2 == 0)
{
even++;
}
else
{
odd++;
}
}
System.out.println(even + " even. " + odd + " odd.");
}
}

import java.util.Scanner;
public class Test2 {
public static void main(String[] args) {
System.out.println("Enter an Integer number:");
Scanner input = new Scanner(System.in);
int num = input.nextInt();
if ( num % 2 == 0 )
System.out.println("Entered number is even");
else
System.out.println("Entered number is odd");
}
}

My suggestion to you is to have a clear separation of your requirements. From your post, you indicate you need to prompt the user for two distinct data items:
How many numbers will be entered (count)
The values to be analyzed
It is a good practice, especially when you are learning, to use meaningful names for your variables. You are using 'n' for a variable name, then reusing it for different purposes during execution. For you, it is obvious it was difficult to figure out what was 'n' at a particular part of the program.
Scanner input = new Scanner (System.in);
int count;
System.out.println ("How many numbers will be entered?");
count = input.nextInt();
//Wait for a valid input
while (count < 1 || count > 100)
{
System.out.println ("ERROR! Valid range 1-100. RE-Enter:");
count = input.nextInt();
}
Additionally, a count of zero should not be valid. It does not make sense to run a program to evaluate zero values (don't bother a program that does nothing). I believe the lowest count should be one instead.
int odd = 0;
int even = 0;
int value;
do
{
System.out.print("Enter a number between 0 and 100: ");
value = input.nextInt();
while (value < 0 || value > 100)
{
System.out.println ("ERROR! Valid range 0-100. RE-Enter:");
value = input.nextInt();
}
if (value % 2 == 0)
{
even++;
}
else
{
odd++;
}
count--; // decrement count to escape loop
} while (count > 0);
System.out.println(even + " even. " + odd + " odd.");
This example uses a do/while loop because in this case, it is OK to enter the loop at least once. This is because you do not allow the user to enter an invalid number of iterations in the first part of the program. I use that count variable directly for loop control (by decrementing its value down to 0), rather than creating another variable for loop control (for instance , 'i').
Another thing, slightly off topic, is that your requirements were not clear. You only indicated that the value was bounded to (inclusive) values between 0 and 100. However, how many times you needed to repeat the evaluation was not really clear. Most people assume 100 was also the upper bound for your counter variable. Because the requirement is not clear, checking a value greater or equal to 1 for the count might be valid, although highly improbable (you don't really want to repeat a million times).
Lastly, you have to pay attention to AND and OR logic in your code. As it was indicated, your second while loop:
while (n >= 0 || n <= 100) {}
Is infinite. Because an OR evaluation only needs one part to evaluate to TRUE, any number entered will allow the loop to continue. Obviously, the intent was not allow values greater than 100. However, entering 150 allows the loop to continue because 150 >= 0. Likewise, -90 also allows the loop to continue because -90 <= 100. This is when pseudocode helps when you are learning. You wanted to express "a VALUE between lower_limit AND upper_limit." If you reverse the logic to evaluate values outside the limit, then you can say " value below lower_limit OR above upper_limit." These pseudocode expressions are very helpful determining which logical operator you need.
I also took the liberty to add a message to prompt the user for a value. Your program expects the user to enter two numbers (count and value) but only one prompt message is provided; unless they enter an out of range value.

extract even numbers from arrayList
ArrayList numberList = new ArrayList<>(Arrays.asList(1,2,3,4,5,6));
numberList.stream().filter(i -> i % 2 == 0).forEach(System.out::println);