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Exiting a loop when there are no more inputs

I am writing some pretty basic java code. The idea is to use a loop to write up to 20 numbers into an array. I want to exit the loop when there are no values left. Right now, my code will write to the array, but I cannot get it to exit the loop without entering a non-integer value. I have read some other posts, but they tend to use string methods, which would make my code kind of bulky. I feel like there is a simple solution to this, but I can't seem to figure it out....
import java.util.Scanner;
public class getArray{
public static void main (String[] args){
Scanner scnr = new Scanner(System.in);
int[]newArray = new int[20];
int newArraySize = 0;
while (scnr.hasNextInt()){
newArray[newArraySize] = scnr.nextInt();
newArraySize += 1;
continue;
}
for (int i = 0; i < newArraySize; i++){
System.out.println("The " + i + " input is " + newArray[i]);
}
}
}

And yet another alternative. Allows for single numerical entry or white-space delimited multiple numerical entry, for example:
--> 1
--> 2
--> 10 11 12 13 14 15 16
--> 20
--> 21
Enter nothing to end data entry and view array contents:
Scanner scnr = new Scanner(System.in);
List<Integer> valuesList = new ArrayList<>();
System.out.println("Enter all the Integer values you would like");
System.out.println("stored into your int[] array. You can enter");
System.out.println("them either singular or multiple values on a");
System.out.println("single line spaced apart with a single white");
System.out.println("space. To stop numerical entry and view your");
System.out.println("array contents just enter nothing.");
System.out.println("============================================");
System.out.println();
String inputLine = "";
while (inputLine.isEmpty()) {
System.out.print("Enter a numerical value: --> ");
inputLine = scnr.nextLine().trim();
// If nothing is supplied then end the 'data entry' loop.
if (inputLine.isEmpty()) {
break;
}
//Is it a string line with multiple numerical values?
if (inputLine.contains(" ") && inputLine.replace(" ", "").matches("\\d+")) {
String[] values = inputLine.split("\\s+");
for (String vals : values) {
valuesList.add(Integer.valueOf(vals));
}
}
//Is it a string line with a single numerical value?
else if (inputLine.matches("\\d+")) {
valuesList.add(Integer.valueOf(inputLine));
}
// If entry is none of the above...
else {
System.err.println("Invalid numerical data supplied (" + inputLine + ")! Try again...");
}
inputLine = "";
}
System.out.println("============================================");
System.out.println();
// Convert List<Integer> to int[]...
int[] newArray = new int[valuesList.size()];
for (int i=0; i < valuesList.size(); i++) {
newArray[i] = valuesList.get(i);
}
// Display the int[] Array
for (int i = 0; i < newArray.length; i++) {
System.out.println("The " + i + " input is " + newArray[i]);
}

If I understand correctly, then you want the input of numbers to be limited to the size of the array?
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
int[] newArray = new int[20];
int newArraySize = 0;
while (newArraySize < newArray.length && scnr.hasNextInt()) {
newArray[newArraySize] = scnr.nextInt();
newArraySize++;
}
for (int i = 0; i < newArraySize; i++) {
System.out.println("The " + i + " input is " + newArray[i]);
}
}

Your while loop condition should be as long as newArraySize is less than the actual size. Here is a fix with some modifications:
Scanner scnr = new Scanner(System.in);
int[]newArray = new int[20];
int newArraySize = 0;
while (newArraySize < newArray.length){
try {
newArray[newArraySize] = scnr.nextInt();
newArraySize++;
}catch(Exception e){
scnr.nextLine();
}
}
for (int i = 0; i < newArraySize; i++){
System.out.println("The " + i + " input is " + newArray[i]);
}

A solution using Java Stream API:
Scanner sc = new Scanner(System.in);
System.out.println("Input 20 numbers: ");
int[] arr = IntStream.generate(sc::nextInt) // create infinite stream generating values supplied by method `nextInt` of the scanner instance
.limit(20) // take only 20 values from stream
.toArray(); // put them into array
System.out.println(Arrays.toString(arr)); // print array contents at once
Also, there's a utility method Arrays.setAll allowing to set array values via IntUnaryOperator:
int[] arr = new int[20];
Arrays.setAll(arr, (x) -> sc.nextInt());

While loop should have condition for Array Length, kindly try below code which will stop taking inputs after 21st input and array elements will be displayed.
import java.util.Scanner;
public class AarrayScanner {
public static void main(String args[]) {
Scanner scnr = new Scanner(System.in);
int[] newArray = new int[20];
int newArraySize = 0;
while (scnr.hasNextInt() && newArraySize < newArray.length) {
newArray[newArraySize] = scnr.nextInt();
newArraySize++;
}
for (int i = 0; i < newArraySize; i++) {
System.out.println("The " + i + " input is " + newArray[i]);
}
}
}

Java: I made a program that accepts input for an integer array & displays values in a table. Trying to recreate this using a string array. Pls. help,

Java is my first programming language, and I'm still unfamiliar with how arrays work. However, I was able to make this program, which accepts user-input for an integer array; it then outputs indexes and values, to show how arrays store numbers. I would like to recreate this program using a string array, to make a table containing a list of friends.
The .length property also confuses me...
Could someone explain the .length property and help me make the string array program work?
Thank you very much.
Here is the working code for the integer array table program
import java.util.*;
public class AttemptArrayTable
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Let me show you how arrays are stored ");
System.out.println("How many numbers do you want your array to
store? ");
int arrayInput [] = new int[scan.nextInt()];
System.out.println("Enter numbers ");
for (int count = 0; count<arrayInput.length; count++)
arrayInput[count] = scan.nextInt();
System.out.println("");
System.out.println("Index\t\tValue");
for (int count2=0; count2<arrayInput.length; count2++)
System.out.println(" [" + count2 + "]"+"\t\t " + arrayInput[count2]);
}
}
Here is the code for the string array program I'm working on
import java.util.*;
public class ArrayTableofFriends
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("How many female friends do you have? ");
String arrayOfFriendsFem [] = new String [scan.nextInt()];
System.out.println("List the name of your female friends");
for(int countF = 0; countF<arrayOfFriendsFem.length; countF++)
arrayOfFriendsFem[countF]= scan.nextLine();
System.out.println("How many male friends do you have? ");
String arrayOfFriendsMale [] = new String [scan.nextInt()];
System.out.println("List the name of your male friends");
for(int countM = 0; countM<=arrayOfFriendsFem.length; countM++)
arrayOfFriendsMale[countM]= scan.nextLine();
System.out.println("How many alien friends do you have? ");
String arrayOfFriendsAliens [] = new String [scan.nextInt()];
System.out.println("List the name of your alien friends");
for(int countA = 0; countA<=arrayOfFriendsFem.length; countA++)
arrayOfFriendsAliens[countA]= scan.nextLine();
{
System.out.println("Female\t\t\t" + "Male\t\t\t" + "Aliens");
for(int countF2 = 0; countF2<arrayOfFriendsFem.length; countF2++)
System.out.println(arrayOfFriendsFem[countF2]);
for(int countM2 = 0; countM2<=arrayOfFriendsMale.length; countM2++)
System.out.println("\t\t\t" + arrayOfFriendsMale[countM2]);
for(int countA2 = 0; countA2<=arrayOfFriendsAliens.length; countA2++)
System.out.println("\t\t\t\t\t\t" +arrayOfFriendsAliens[countA2]);
}
}

.length property stores number of elements in the array. But elements are starting from 0. So, when .length = 1, then there is only one element in the array, with index 0.
It seems in your String arrays program in the for loop the <= should be changed to <
Like this:
for (int countA = 0; countA < arrayOfFriendsFem.length; countA++)

How to take single array input from user?

In the following code i marked the line that doesn't work.
Can someone explain me why this doesn't work?
import java.util.Scanner;
public class ArrayLength {
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
System.out.println("Please enter the array : ");
double[] userArray = myScanner.nextDouble();//This line doesn't work
}
}

I guess you are trying to set a double array from a line-separated input. If so, you could use something like this:
Scanner myScanner = new Scanner(System.in);
System.out.println("Please enter the array : ");
String strScan = myScanner.nextLine();
String[] aScan = strScan.split(" ");
double[] userArray = new double[aScan.length];
int i = 0 ;
for (String str : aScan) {
userArray[i] = Double.parseDouble(str);
i++;
}

If you are expecting the user input to be located on exactly one line and you are sure that all the values (separated by a whitespace) could be parsed as Double I do recommend using the following statement:
double[] userArray = Arrays.stream(myScanner.nextLine().split(" "))
.mapToDouble(Double::parseDouble)
.toArray();
Read whole next line as string, split it by whitespace, and then do parse each value into double.
If you only need to read a single double value and you are required to store it into an array then you could simply use the Array Initializer like this:
double[] userArray = {myScanner.nextDouble()};
This way userArray will have 1 element in total and it's first and only value will be the user input.

You have to define array index in int, then only get double input
public class Example {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
//Decide array length
System.out.print("Please enter the array : ");
int num = Integer.parseInt(scan.nextLine());
//Create a double array to store values
double userArray[] = new double[num];
for (int i = 0; i < userArray.length; i++) {
System.out.print("Enter value " + (i + 1) + " : ");
userArray[i] = scan.nextDouble(); // you can store input with double datatype now
}
//Now display one by one
for (int i = 0; i < userArray.length; i++) {
System.out.print("Value are " + (i + 1) + " : ");
System.out.print(userArray[i] + "\n");
}
}
}
If you don't want to take input as array
double num= myScanner.nextDouble();

myScanner.nextDouble() will output a single double instead of an array of doubles. So you would need to set that double equal to a specific index in the array instead of trying to set the whole array equal to a single double. I would suggest utilizing a for loop if you want to accept multiple doubles into the array.
For Example:
for(int x = 0; x < userArray.length; x++)
{
userArray[x] = myScanner.nextDouble(); // x in this scenario is a specific position in the array
}
Also if the user input is formatted with a space between each double (i.e. 1.0 2.0 3.0 4.0 etc) myScanner.nextDouble(); will take the first double then go through the for loop again and take the next double etc. This is useful because the user input can all be on one line so the user can input the entire array at once.

java user-defined array (and user-defined array size) returning [null, null, null, ...]

This is my first question on this site, I'm running this on NetBeans 8.0.2 and trying to print out my user-defined array but it keeps returning null values. For example if you say there are 2 employees and enter both of their names, it will return [null, null]
How to fix this error? I'm a novice.
import java.util.Scanner;
import java.text.DecimalFormat;
import java.util.Arrays;
class Tips_Calculation2
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.print("How many employees for the week?: ");
int numberOfEmps = scan.nextInt();
// counter for the if statement that should return all employees from the array
int counter = numberOfEmps;
int[] nOEarray = new int[numberOfEmps];
System.out.println("\nEnter names of workers up to the entered amount (" + numberOfEmps + "):");
for(int i = 1; i <= numberOfEmps; i++)
{
String nameCycler = scan.next();
String[] namesArray = new String[i];
if(counter == i)
{
System.out.println(Arrays.toString(namesArray));
}
}
}
}
Disregard import java.text.DecimalFormat as I plan to use this import later on in my code. Thank you in advance to anyone who is kind/smart enough to respond.

First of all you never put your nameCycler to array. Second of all you create your namesArray every iteration which I think is wrong.

You're creating a brand new (full of null) array namesArray on every pass through the loop--and then never assigning anything to it. I think you're looking for something like this instead. Note that Java indexes from zero, not one.
String[] names = new String[numberOfEmps]
for(int i = 0; i < names.length; i++) {
names[i] = scanner.next();
}
System.out.println(Arrays.toString(names));

First of all, you should initialise the array outside of your loop. Secondly, you forgot to set the name to the array value(s).
Try this:
import java.util.Scanner;
import java.text.DecimalFormat;
import java.util.Arrays;
class Tips_Calculation2 {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("How many employees for the week?: ");
int numberOfEmps = scan.nextInt();
int[] nOEarray = new int[numberOfEmps];
System.out.println("\nEnter names of workers up to the entered amount (" + numberOfEmps + "):");
String[] namesArray = new String[numberOfEmps];
for (int i = 0; i < numberOfEmps; i++) {
namesArray[i] = scan.next();
}
System.out.println(Arrays.toString(namesArray));
}
}

Replace
for(int i = 1; i <= numberOfEmps; i++)
{
String nameCycler = scan.next();
String[] namesArray = new String[i];
if(counter == i)
{
System.out.println(Arrays.toString(namesArray));
}
}
With
String[] namesArray = new String[numberOfEmps];
for(int i = 0; i < numberOfEmps; i++)
{
namesArray[i] = scan.next();
}
System.out.println(Arrays.toString(namesArray));
And see whether it works.

You never assign the name to the array and in every iteration you define the array new:
String[] namesArray = new String[numberOfEmps];
for(int i = 1; i <= numberOfEmps; i++)
{
String nameCycler = scan.next();
namesArray [i] = nameCycler ;
if(counter == i)
{
System.out.println(Arrays.toString(namesArray));
}
}

Added comments in the code to point out changes.
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("How many employees for the week?: ");
int numberOfEmps = scan.nextInt();
// removed 'nOEarray' and 'counter'
if (numberOfEmps > 0) {
System.out.println("\nEnter names of workers up to the entered amount (" + numberOfEmps + "):");
// initializing 'namesArray' outside for loop.
String[] namesArray = new String[numberOfEmps];
for(int i = 0; i < numberOfEmps; i++) { // initialized with 0 and updated condition with '<'
namesArray[i] = scan.next(); // assigning value to 'i'th position of namesArray
}
System.out.println(Arrays.toString(namesArray)); // Printing array outside for loop
}
}

"How to fix this error" not. This is not an error.
String[] namesArray = new String[i]; // step one, you declare an array of Strings
// which you don't initialize
if(counter == i)
{
System.out.println(Arrays.toString(namesArray));
//you print all the (non-initialized) elements of namesArray
//since you didn't initialize the elements, it takes the default value, which is null
}
fill the elements of the array with Strings before trying to print them.

How to read multiple Integer values from a single line of input in Java?

I am working on a program and I want to allow a user to enter multiple integers when prompted. I have tried to use a scanner but I found that it only stores the first integer entered by the user. For example:
Enter multiple integers: 1 3 5
The scanner will only get the first integer 1. Is it possible to get all 3 different integers from one line and be able to use them later? These integers are the positions of data in a linked list I need to manipulate based on the users input. I cannot post my source code, but I wanted to know if this is possible.

I use it all the time on hackerrank/leetcode
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String lines = br.readLine();
String[] strs = lines.trim().split("\\s+");
for (int i = 0; i < strs.length; i++) {
a[i] = Integer.parseInt(strs[i]);
}

Try this
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNext()) {
if (in.hasNextInt())
System.out.println(in.nextInt());
else
in.next();
}
}
By default, Scanner uses the delimiter pattern "\p{javaWhitespace}+" which matches at least one white space as delimiter. you don't have to do anything special.
If you want to match either whitespace(1 or more) or a comma, replace the Scanner invocation with this
Scanner in = new Scanner(System.in).useDelimiter("[,\\s+]");

You want to take the numbers in as a String and then use String.split(" ") to get the 3 numbers.
String input = scanner.nextLine(); // get the entire line after the prompt
String[] numbers = input.split(" "); // split by spaces
Each index of the array will hold a String representation of the numbers which can be made to be ints by Integer.parseInt()

Scanner has a method called hasNext():
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext())
{
System.out.println(scanner.nextInt());
}

If you know how much integers you will get, then you can use nextInt() method
For example
Scanner sc = new Scanner(System.in);
int[] integers = new int[3];
for(int i = 0; i < 3; i++)
{
integers[i] = sc.nextInt();
}

Java 8
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
int arr[] = Arrays.stream(in.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();

Here is how you would use the Scanner to process as many integers as the user would like to input and put all values into an array. However, you should only use this if you do not know how many integers the user will input. If you do know, you should simply use Scanner.nextInt() the number of times you would like to get an integer.
import java.util.Scanner; // imports class so we can use Scanner object
public class Test
{
public static void main( String[] args )
{
Scanner keyboard = new Scanner( System.in );
System.out.print("Enter numbers: ");
// This inputs the numbers and stores as one whole string value
// (e.g. if user entered 1 2 3, input = "1 2 3").
String input = keyboard.nextLine();
// This splits up the string every at every space and stores these
// values in an array called numbersStr. (e.g. if the input variable is
// "1 2 3", numbersStr would be {"1", "2", "3"} )
String[] numbersStr = input.split(" ");
// This makes an int[] array the same length as our string array
// called numbers. This is how we will store each number as an integer
// instead of a string when we have the values.
int[] numbers = new int[ numbersStr.length ];
// Starts a for loop which iterates through the whole array of the
// numbers as strings.
for ( int i = 0; i < numbersStr.length; i++ )
{
// Turns every value in the numbersStr array into an integer
// and puts it into the numbers array.
numbers[i] = Integer.parseInt( numbersStr[i] );
// OPTIONAL: Prints out each value in the numbers array.
System.out.print( numbers[i] + ", " );
}
System.out.println();
}
}

There is more than one way to do that but simple one is using String.split(" ")
this is a method of String class that separate words by a spacial character(s) like " " (space)
All we need to do is save this word in an Array of Strings.
Warning : you have to use scan.nextLine(); other ways its not going to work(Do not use scan.next();
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
now we need to convert these strings to Integers. create a for loop and convert every single index of stringArray :
for (int i = 0; i < stringsArray.length; i++) {
int x = Integer.parseInt(stringsArray[i]);
// Do what you want to do with these int value here
}
Best way is converting the whole stringArray to an intArray :
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
now do any proses you want like print or sum or... on intArray
The whole code will be like this :
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
}
}

This works fine ....
int a = nextInt();
int b = nextInt();
int c = nextInt();
Or you can read them in a loop

Using this on many coding sites:
CASE 1: WHEN NUMBER OF INTEGERS IN EACH LINE IS GIVEN
Suppose you are given 3 test cases with each line of 4 integer inputs separated by spaces 1 2 3 4, 5 6 7 8 , 1 1 2 2
int t=3,i;
int a[]=new int[4];
Scanner scanner = new Scanner(System.in);
while(t>0)
{
for(i=0; i<4; i++){
a[i]=scanner.nextInt();
System.out.println(a[i]);
}
//USE THIS ARRAY A[] OF 4 Separated Integers Values for solving your problem
t--;
}
CASE 2: WHEN NUMBER OF INTEGERS in each line is NOT GIVEN
Scanner scanner = new Scanner(System.in);
String lines=scanner.nextLine();
String[] strs = lines.trim().split("\\s+");
Note that you need to trim() first: trim().split("\\s+") - otherwise, e.g. splitting a b c will emit two empty strings first
int n=strs.length; //Calculating length gives number of integers
int a[]=new int[n];
for (int i=0; i<n; i++)
{
a[i] = Integer.parseInt(strs[i]); //Converting String_Integer to Integer
System.out.println(a[i]);
}

created this code specially for the Hacker earth exam
Scanner values = new Scanner(System.in); //initialize scanner
int[] arr = new int[6]; //initialize array
for (int i = 0; i < arr.length; i++) {
arr[i] = (values.hasNext() == true ? values.nextInt():null);
// it will read the next input value
}
/* user enter = 1 2 3 4 5
arr[1]= 1
arr[2]= 2
and soo on
*/

It's working with this code:
Scanner input = new Scanner(System.in);
System.out.println("Enter Name : ");
String name = input.next().toString();
System.out.println("Enter Phone # : ");
String phone = input.next().toString();

A simple solution can be to consider the input as an array.
Scanner sc = new Scanner(System.in);
int n = sc.nextInt(); //declare number of integers you will take as input
int[] arr = new int[n]; //declare array
for(int i=0; i<arr.length; i++){
arr[i] = sc.nextInt(); //take values
}

You're probably looking for String.split(String regex). Use " " for your regex. This will give you an array of strings that you can parse individually into ints.

Better get the whole line as a string and then use StringTokenizer to get the numbers (using space as delimiter ) and then parse them as integers . This will work for n number of integers in a line .
Scanner sc = new Scanner(System.in);
List<Integer> l = new LinkedList<>(); // use linkedlist to save order of insertion
StringTokenizer st = new StringTokenizer(sc.nextLine(), " "); // whitespace is the delimiter to create tokens
while(st.hasMoreTokens()) // iterate until no more tokens
{
l.add(Integer.parseInt(st.nextToken())); // parse each token to integer and add to linkedlist
}

Using BufferedReader -
StringTokenizer st = new StringTokenizer(buf.readLine());
while(st.hasMoreTokens())
{
arr[i++] = Integer.parseInt(st.nextToken());
}

When we want to take Integer as inputs
For just 3 inputs as in your case:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a,b,c;
a = scan.nextInt();
b = scan.nextInt();
c = scan.nextInt();
For more number of inputs we can use a loop:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a[] = new int[n]; //where n is the number of inputs
for(int i=0;i<n;i++){
a[i] = scan.nextInt();
}

This method only requires users to enter the "return" key once after they have finished entering numbers:
It also skips special characters so that the final array will only contains integers
ArrayList<Integer> nums = new ArrayList<>();
// User input
Scanner sc = new Scanner(System.in);
String n = sc.nextLine();
if (!n.isEmpty()) {
String[] str = n.split(" ");
for (String s : str) {
try {
nums.add(Integer.valueOf(s));
} catch (NumberFormatException e) {
System.out.println(s + " cannot be converted to Integer, skipping...");
}
}
}

//Get user input as a 1 2 3 4 5 6 .... and then some of the even or odd number like as 2+4 = 6 for even number
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int evenSum = 0;
int oddSum = 0;
while (n > 0) {
int last = n % 10;
if (last % 2 == 0) {
evenSum += last;
} else {
oddSum += last;
}
n = n / 10;
}
System.out.println(evenSum + " " + oddSum);
}
}

if ur getting nzec error, try this:
try{
//your code
}
catch(Exception e){
return;
}

i know it's old discuss :) i tested below code it's worked
`String day = "";
day = sc.next();
days[i] = Integer.parseInt(day);`