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What is the best way to read user inputs via scanner?

I use some approaches similar to the following one in Java:
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int[] a= new int[3];
//assign inputs
for (int i=0;i<3;i++)
a[i] = scan.nextInt();
scan.close();
//print inputs
for(int j=0;j<3;j++)
System.out.println(a[j]);
}
However, generally the first input parameter is length and for this reason I use an extra counter (c) in order to distinguish the first element. When using this approach, the scanner does not read inputs one by one and checking the first and other elements in two blocks seems to be redundant.
// input format: size of 3 and these elements (4, 5, 6)
// 3
// 4 5 6
public static void getInput() {
int n = 0; //size
int c = 0; //counter for distinguish the first index
int sum = 0; //
int[] array = null;
Scanner scan = new Scanner(System.in);
System.out.println("Enter size:");
//block I: check the first element (size of array) and assign it
if (scan.nextInt() <= 0)
System.out.println("n value must be greater than 0");
else {
n = scan.nextInt();
array = new int[n];
}
System.out.println("Enter array elements:");
//block II: check the other elements adn assign them
while(scan.hasNextInt() && c<n) {
if (scan.nextInt() >= 100) {
System.out.println("Array elements must be lower than 100");
} else {
array[c] = scan.nextInt();
c++;
}
}
scan.close();
int sum = 0;
for (int j = 0; j < n; j++) {
sum += array[j];
}
System.out.println("Sum = " + sum);
}
My question is "how can I modify this approach with a single block (while and for loop inside while)? I tried 5-6 different variations but none of them works properly?"

Hope this helps,
public static void getInput() {
int n; //size
int c = 0; //counter for distinguish the first index
int sum = 0; //
int[] array;
Scanner scan = new Scanner(System.in);
System.out.println("Enter size:");
//check the first element (size of array) and assign it
n = scan.nextInt();
while(n <= 0)
{
System.out.println("n value must be greater than 0");
System.out.println("Enter size:");
n = scan.nextInt();
}
array = new int[n];
System.out.println("Enter array elements:");
// check the other elements and assign them
while(c<n) {
int num = scan.nextInt();
if (num >= 100) {
System.out.println("Array elements must be lower than 100");
} else {
array[c++] = num;
}
}
scan.close();
for (int j = 0; j < n; j++) {
sum += array[j];
}
System.out.println("Sum = " + sum);
}
Output:
Enter size:
-1
n value must be greater than 0
Enter size:
4
Enter array elements:
1
2
3
4
Sum = 10

I've optimized your code and fixed some bug.
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter size:");
int n = scan.nextInt();
if (n <= 0) {
System.out.println("n value must be greater than 0");
return; // need to break from here
}
int c = 0;
int sum = 0; // no need for array
System.out.println("Enter array elements:");
// check the other elements and assign them
while (c++ < n) {
int next = scan.nextInt();
if (next >= 100) {
System.out.println("Array elements must be lower than 100");
c--; // ensure can reenter the number
} else {
sum += next;
}
}
scan.close();
System.out.println("Sum = " + sum);
}

Calculate the multiplication of an ArrayList

I'm so stuck of how to get the answer below, this question required to use the ArrayList and recursion as well. Code below is what I've got so far, and now I'm so stuck. I've done a lot of research but still not find the answer. If you can, you can explain and provide some answer, THANK YOU.
The elements of your array are: 1 2 3 4 5 6 -1
The multiplication of {1, 2, 3, 4, 5, 6} is 720.
Also, if the user enters the negative number, the ArrayList won't multiply that number. Please help.
public class Arraylist{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("The elements of your array are: ");
int num = scan.nextInt();
ArrayList<Integer> element = new ArrayList<Integer>();
while (true){
element.add(scan.nextInt());
}
}
}

Considering negative value terminate loop
Scanner scan = new Scanner(System.in);
System.out.print("The elements of your array are: ");
ArrayList<Integer> element = new ArrayList<Integer>();
int ans = 1;
while (true){
int num = scan.nextInt();
if(num < 0)
break;
element.add(num);
ans *= num;
}
System.out.println(ans);

Define a recursive function to get the product.
public class Arraylist{
public static int getProduct(ArrayList<Integer> elements, int index) {
if(index == elements.size() ) return 1;
else
return (elements.get(index) > 0)?
elements.get(index): 1 *
getProduct(elements, i+1);
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("Enter number of elements:");
int num = scan.nextInt(), prod = 1;
ArrayList<Integer> elements = new ArrayList<Integer>();
System.out.println("Enter " + num + " elements:");
for(int i = 0; i < num; i++) {
elements.add(scan.nextInt());
}
prod = getProduct(elements);
System.out.println("Product is: " + prod);
}

About saving and printing distinct numbers in an array

before you help me this is a homework assignment, i have most of all of it done but there is one thing that i cant figure out, 0 doesn't get detected at all. This means if i input 0-9 into the array it will tell me there is only 9 distinct numbers when really there should be 10 and it will print out all the numbers but 0. Can anyone see the problem and please explain it to me becuase i need to understand it.
package javaproject.pkg2;
import java.util.Scanner;
public class JavaProject2 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] numArray = new int[10];
int d = 0;
System.out.println("Enter Ten Numbers: ");
for(int i = 0; i < numArray.length; i++){
int num = input.nextInt();
if(inArray(numArray,num,numArray.length)){
numArray[i] = num;
d++;
}
}
System.out.println("The number of distinct numbers is " + d);
System.out.print("The distinct numbers are: ");
for(int i = 0; i < d; i++){
System.out.print(numArray[i] + " ");
}
}
public static boolean inArray(int[] array, int searchval, int numvals){
for (int i =0; i < numvals; i++){
if (searchval == array[i]) return false;
}
return true;
}
}

You can use a set to identify distinct values:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
Set<Integer> distinctNumbers = new LinkedHashSet<>();
System.out.println("Enter ten Numbers: ");
for (int i = 0; i < 10; i++) {
int number = input.nextInt();
distinctNumbers.add(number);
}
System.out.println("The number of distinct numbers is " + distinctNumbers.size());
System.out.print("The distinct numbers are: ");
for (Integer number : distinctNumbers){
System.out.print(number + " ");
}
}
If a value already exists in a set, it can't be added again. Arrays are not the best fit for your problem, since they must be initialized with a fixed size and you don't know how many distinct values the user will inform.

Take a look at numArray after int[] numArray = new int[10]; - it is initialized with zeros.

How to return the Max Value and Max Count from a user input

I'm trying to get both, the largest number and the largest occurring number, from a user input. The problem with my code is it only returns the first value of the array.
public class CountMax {
public static void main(String [] args) {
//Create scanner object
Scanner input = new Scanner(System.in);
//Obtain user input
System.out.println("Enter numbers: ");
int num = input.nextInt();
int array[] = new int[num];
//loop through array
int max = array[0];
int count = 1;
for (int i = 0; i < array.length; i++) {
array[i] = num;
if(array[i] > max) {
max = array[i];
count = 1;
} else if(array[i] == max) {
count++;
}
}
//output results
System.out.println("The largest number is " + max);
System.out.println("The occurrence count of the largest number is " + count);
}}

I know this post is old, but Wyatt Lowery's solution is incorrect, just in case someones stumbles upon it from Google just like I did. You cannot count the number of max values in an array in the same loop like that until you have found the max value.
Example using Wyatt's class: 2 is obviously an incorrect answer.
Enter numbers:
1, 2, 3, 4, 5, 5, 7
The largest number is 7
The occurrence count of the largest number is 2
I would do:
int max = array[0];
int sum = 0;
for(int i = 1; i < array.length; i++) {
if(array[i] > max) max = array[i];
}
for(int i = 0; i < array.length; i++) {
if(array[i]==max) sum++;
}

One problem I noticed:
int num = input.nextInt();
When you do this, it is only going to take the first int (Meaning, only 1 number) As well when you are creating your array int array[] = new int[num], you are creating an array with the SIZE of num, and not actually creating an array with the VALUES of num. (Even though num is only a single number) To actually create an array of numbers, do something like this:
System.out.pritnln("Enter in numbers:");
String[] array = input.nextLine().split(", ");
An example input would be: "13, 12, 14, 14". Then the contents of the array would be those terms (And would remove spaces & commas). Your program should look something like this when finished:
public class CountMax {
public static void main(String [] args) {
//Create scanner object
Scanner input = new Scanner(System.in);
//Obtain user input
System.out.println("Enter numbers: ");
String[] array = input.nextLine().split(", ");
//Loop through array
int max = Integer.parseInt(array[0]);
int count = 0;
for (int i = 0; i < array.length; i++) {
if(Integer.parseInt(array[i]) > max) {
max = Integer.parseInt(array[i]);
} else if(Integer.parseInt(array[i]) == max) {
count++;
}
}
//Output
System.out.println("The largest number is " + max);
System.out.println("The occurrence count of the largest number is " + count);
}
}
Hope this helped :-)

Think more carefully about each step you need to take.
Do you know how many numbers will be entered by the user?
Right now you are only taking in one number because you are not looping on the input
int num = input.nextInt();
int array[] = new int[num];
Here, you are creating an array the size of whatever number the user entered. This is a correct approach, more typical of C, if the user will tell you "I will enter 10 numbers" and then enters the 10 numbers. This is convenient because you will know to loop 10 times, and you will need to count a maximum of 10 different numbers.
If we don't know how many numbers will be entered you will need to loop until EOF.. something like
while(input.hasNext()) {
int currentInt = input.next();
...
}
Now you have to consider how you will be counting these items.
I hope this gives you some things to think about towards your solution..

Taking multiline inputs in java command line

The problem I'm trying to solve is given an integer N find the digits in this number that exactly divide N(division that leaves 0 as remainder) and display their count. For N=24, there are 2 digits − 2 & 4. Both of these digits exactly divide 24. So our answer is 2. The input format is The first line contains T (number of test cases) followed by T lines (each containing an integer N).
Here's my code
public static void main(String[] args) throws IOException {
System.out.println("Please enter your inputs");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line;
ArrayList<String> arr = new ArrayList<String>();
int i=0;
while ((line = br.readLine()) != null && line.length() != 0){
arr.add(line);
i++;
}
if(Integer.parseInt(args[0]) != (args.length -1)){
System.out.println("Wrong number of inputs");
}else{
for(int j = 1; j< args.length; j++){
System.out.println(findDivisor(Integer.parseInt(args[j])));
}
}
}
public static int findDivisor(int n){
int count = 0;
String s = Integer.toString(n);
char[] c= s.toCharArray();
for(int i = 0; i< c.length; i++){
String temp = Character.toString(c[i]);
int num = Integer.parseInt(s);
if(num == 0)
count += 0;
else if(n%num == 0){
count +=1;
}
}
return count;
}
On adding an Arraylist to read to inputs, the program goes into an infinite loop it seems. As in based on the first input I need to take the number of inputs and then process. As in if the first input is 2, my program should await 2 more command line inputs and on the third press of enter run. How do I invoke that functionality into this code.

Try using the Scanner class:
import java.util.Scanner;
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
// Read in T.
int T = sc.nextInt();
// Read in T integers, for each print the number of digit divisors.
for (int i = 0; i < T; i++){
int n = sc.nextInt()
System.out.println(findDivisor(n));
}
}
If you want to wait until all input is in first, create an array of size T to keep track of your integers:
import java.util.Scanner;
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
// Read in T.
int T = sc.nextInt();
int[] myNumbers = new int[T];
// Read in all input, and calculate the number of digit divisors.
for (int i = 0; i < T; i++){
int n = sc.nextInt()
myNumbers[i] = findDivisor(n);
}
// For each input, print out the number of digit divisors.
System.out.println("Number of digit divisors:");
for (int i = 0; i < T; i++){
System.out.println(myNumbers[i]);
}
}