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Array *not throwing out of bounds exception

I'm trying to learn about exception handling. I can't seem to get
String[] a = names(scnr); To throw an out of bounds exception when it goes beyond 3 elements. I know, most people hate the out of bounds error and I'm trying to make it happen and for the life of me I cannot figure out what I'm doing wrong. Been at it all day and googled all kinds of stuff. But I cannot seem to find exactly what I'm looking for. So I could use some help and perspective.
So I'm inputting a full string that I'm delimiting (trim and splitting) based on commas and spaces and then the pieces are being stored into an array (String []name), then passed to main to be output with String[] a. So it's not erroring when I go beyond 3 elements no matter how I do it. I can just not display anything beyond a[4]. But that's not really what I'm trying to do. Its my first java class so be gentle haha.
Any suggestions?
import java.util.*;
public class ReturnArrayExample1
{
public static void main(String args[])
{
Scanner scnr = new Scanner(System.in);
String[] a = names(scnr);
for (int i = 0; i < 3; i++)
{
System.out.println(a[i] + " in index[" + i + "].");
}
scnr.close();
}
public static String[] names(Scanner scnr)
{
String[] name = new String[3]; // initializing
boolean run = true;
do
{
try
{
System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
String rawData = scnr.nextLine();
if(rawData.isEmpty())
{
System.err.println("Nothing was entered!");
throw new Exception();
}
else
{
name = rawData.trim().split("[\\s,]+");
run = false;
}
}
catch(ArrayIndexOutOfBoundsException e)
{
System.err.println("Input is out of bounds!\nUnsuccessful!");
}
catch(Exception e)
{
System.err.println("Invalid entry!\nUnsuccessful!");
}
}
while(run == true);
System.out.println("Successful!");
scnr.close();
return name;
}
}

If I understand you correctly, you want to throw an ArrayOutOfBoundsException if the names array does not contain exactly 3 elements. The following code is the same as the one you wrote with an if-statement to do just that.
import java.util.*;
public class ReturnArrayExample1
{
public static void main(String args[])
{
Scanner scnr = new Scanner(System.in);
String[] a = names(scnr);
for (int i = 0; i < 3; i++)
{
System.out.println(a[i] + " in index[" + i + "].");
}
scnr.close();
}
public static String[] names(Scanner scnr)
{
String[] name = new String[3]; // initializing
boolean run = true;
do
{
try
{
System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
String rawData = scnr.nextLine();
if(rawData.isEmpty())
{
System.err.println("Nothing was entered!");
throw new Exception();
}
else
{
name = rawData.trim().split("[\\s,]+");
if (name.length != 3) {
throw new ArrayIndexOutOfBoundsException();
}
run = false;
}
}
catch(ArrayIndexOutOfBoundsException e)
{
System.err.println("Input is out of bounds!\nUnsuccessful!");
}
catch(Exception e)
{
System.err.println("Invalid entry!\nUnsuccessful!");
}
}
while(run == true);
System.out.println("Successful!");
scnr.close();
return name;
}
}

If you want java to throw an ArrayIndexOutOfBoundException you have to preserve the created names instance and let java copy the array into your names array:
String[] names=new String[3];
String[] rawElements=rawData.trim().split("[\\s,]+");
System.arraycopy(rawElements, 0, names, 0, rawElements.length);
output:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
at java.lang.System.arraycopy(Native Method)
at stackoverflow.OutOfBound.main(OutOfBound.java:8)

As far as I understand, you are expecting an exception (ArrayIndexOutOfBoundsException) to the thrown at line
name = rawData.trim().split("[\\s,]+");
with an argument that the size of array (name) is fixed to 3, and when if the input is beyond 3 then the exception must be thrown; which is not the case.
The reason is in the way assignment happens in java. When you declare String[] name = new String[3];, then an object is created in java heap and its reference is assigned to variable name which is in stack memory.
And when this line name = rawData.trim().split("[\\s,]+"); gets executed then a new array object is created in heap and the variable name starts pointing to the newly created array object on heap. Note: the old object will get available for garbage collection after some time.
This eventually changes the length of the array variable (name) and you do not get any ArrayIndexOutOfBoundsException.
You can understand this more clearly by printing the object on console, like System.out.println(name); after its initialisation and post its assignment.
I will also suggest you to refer this link (https://books.trinket.io/thinkjava2/chapter7.html#elements) to understand how array are created, initialised and copied etc..
Code with system.out commands (for understanding)
import java.util.Scanner;
public class ReturnArrayExample1 {
public static void main(String args[]) {
Scanner scnr = new Scanner(System.in);
String[] a = names(scnr);
System.out.println("Variable (a) is referring to > " + a);
for (int i = 0; i < 3; i++) {
System.out.println(a[i] + " in index[" + i + "].");
}
scnr.close();
}
public static String[] names(Scanner scnr) {
String[] name = new String[3]; // initializing
System.out.println("Variable (name) is referring to > " + name);
boolean run = true;
do {
try {
System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
String rawData = scnr.nextLine();
if (rawData.isEmpty()) {
System.err.println("Nothing was entered!");
throw new Exception();
} else {
name = rawData.trim().split("[\\s,]+");
System.out.println("Now Variable (name) is referring to > " + name);
run = false;
}
} catch (ArrayIndexOutOfBoundsException e) {
System.err.println("Input is out of bounds!\nUnsuccessful!");
} catch (Exception e) {
System.err.println("Invalid entry!\nUnsuccessful!");
}
} while (run == true);
System.out.println("Successful!");
scnr.close();
return name;
}
}
I you want to throw exception when input is more than 3 then there are many ways to do it. One suggestion from #mohamedmoselhy.com is also decent.

read lines from external file and store elements in array

I am new here so please show some patience. I am trying to read the data from an external file and store the info in 2 arrays.
The file looks like this:
0069 723.50
0085 1500.00
0091 8237.31
I am using 2 scanners to read the input and I think they work ok because when I try to print, the result looks ok.
My first problem is that I am able to read the first numbers on the list using nextInt(), but cannot use nextDouble() for the double ones as I get the "java.util.InputMismatchException" message. For that reason I read it as a String. The part with the other two scanners is supposed to do what the first parts should do, for a different input file, but the problem is the same.
My next and biggest problem, until now, is that am not able to store the values from the two columns in two distinct arrays. I have tried several ways (all commented) but all fail. Please help and thanks.
Here is my code:
import ui.UserInterfaceFactory;
import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;
import ui.UIAuxiliaryMethods;
public class Bank {
static final int MAX_NUMBER_OF_ACCOUNTS = 50;
PrintStream out;
Bank(){
UserInterfaceFactory.enableLowResolution(true);
out = new PrintStream(System.out);
}
void readFiles(){
Scanner balanceFile = UIAuxiliaryMethods.askUserForInput().getScanner();
while(balanceFile.hasNextLine()){
String balance_Line = balanceFile.nextLine();
Scanner accountsFile = new Scanner(balance_Line);
int account = accountsFile.nextInt(); //works
out.printf("%04d ",account);
/*int [] accounts_array = new int [MAX_NUMBER_OF_ACCOUNTS]; //does not store the values properly
int account = accountsFile.nextInt();
for(int j=0; j < accounts_array.length; j++){
accounts_array[j] = account;
}*/
/*int [] accounts_array = new int [MAX_NUMBER_OF_ACCOUNTS]; //java.util.InputMismatchException
for(int j=0; j < accounts_array.length; j++){
accounts_array[j] = accountsFile.nextInt();
//out.printf("%04d \n",accounts_array[j]);
}*/
String balance = accountsFile.nextLine(); //problem declaring balance as a double
out.printf("%s\n",balance);
/*String [] balance_array = new String [MAX_NUMBER_OF_ACCOUNTS]; //java.util.NoSuchElementException
for(int j=0; j < balance_array.length; j++){
accountsFile.useDelimiter(" ");
balance_array[j] = accountsFile.next();
//out.printf("%04d \n",accounts_array[j]);
}*/
}
Scanner mutationsFile = UIAuxiliaryMethods.askUserForInput().getScanner();
while(mutationsFile.hasNext()){
String mutation_Line = mutationsFile.nextLine();
Scanner mutatedAccountsFile = new Scanner(mutation_Line);
int mutated_account = mutatedAccountsFile.nextInt();
out.printf("%04d ",mutated_account);
int action = mutatedAccountsFile.nextInt(); //deposit or withdrawal
/*if (action == 1){
}else{
}*/
out.printf(" %d ",action);
/*Double amount = mutatedAccountsFile.nextDouble();
out.printf(" %5.2f ",amount);*/
String amount = mutatedAccountsFile.nextLine();
out.printf("%s\n",amount);
}
}
void start(){
new Bank();readFiles();
}
public static void main(String[] args) {
new Bank().start();
}
}

The InputMismatchException occurs because you try to read a double using the nextInt() function. To solve this issue, you can first read the tokens as Strings using the next() function and convert them appropriately.
while(mutationsFile.hasNext()){
mutation_Line = mutationsFile.next();
if(mutation_Line.indexOf(".") == -1)
//token is int
else
//token is double
}
Since you already know what the contents of the two columns are, you can store the integers and doubles in two lists and then, if you want, get them into an array.
List<Integer> intList = new ArrayList<Integer>();
List<Double> doubleList = new ArrayList<Double>();
Now replace the if statements in the first snippet with this:
if(mutation_Line.indexOf(".") == -1)
intList.add(new Integer(Integer.parseInt(mutation_Line)));
else
doubleList.add(new Double(Double.parseDouble(mutation_Line)));
In the end, you can get them into arrays:
Object[] intArr = intList.toArray(),
doubleArr = doubleList.toArray();
//display the contents:
for(int i=0; i<intArr.length; i++)
out.printf("%04d\t%.2f\n", Integer.parseInt(intArr[i].toString()),
Double.parseDouble(doubleArr[i].toString()));
OUTPUT:
0069 723.50
0085 1500.00
0091 8237.31

First off, you don't need to use 2 scanners. The Scanner object is simply reading your file, one scanner is plenty to accomplish the task of reading a file.
If you're trying to read the integers/doubles from file and are having trouble with nextInt() and nextDouble(), consider a different approach to parsing (e.g. parse the line into a string, split the line into 2 parts based on a space character, then trim both resulting strings and convert to respective integers/doubles).
Now back to the Scanner parsing the two values, remember first that when you use a next() or nextInt(), etc. those methods consume the next respective token. So parsing a line as a string from the file into another Scanner object is redundant and unnecessary in this case.
If you know your max number of accounts, and it's simply 50, then go ahead an allocate that prior to the while loop.
Here's an alternative approach with the code you posted.
public class App {
static int MAX_NUMBER_OF_ACCOUNTS = 50;
static PrintStream out;
static void readFiles() {
Scanner balanceFile = null;
try {
balanceFile = new Scanner(new File("C:\\Users\\Nick\\Desktop\\test.txt"));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
if (balanceFile == null)
return;
int [] accounts_array = new int [MAX_NUMBER_OF_ACCOUNTS];
double [] balance_array = new double [MAX_NUMBER_OF_ACCOUNTS];
int currentIndex = 0;
while (balanceFile.hasNextLine()) {
int account = balanceFile.nextInt();
double balance = balanceFile.nextDouble();
System.out.print("acc = " + account + " ");
System.out.println("bal = " + balance);
//out.printf("%04d ", account);
accounts_array[currentIndex] = account;
//out.printf("%s\n", balance);
balance_array[currentIndex] = balance;
currentIndex++;
}
balanceFile.close();
}
static void start() {
readFiles();
}
public static void main(String[] args) {
start();
}
}
Please note the excessive use of static could also be avoided in the future, but for the sake of the example it spread like the plague.
As you can see in the logic leading up to the while loop, the scanner object is made from a file I copied your example data into a file on my desktop. The arrays are allocated prior to the while loop (note: see #progy_rock and their use of ArrayList's - may help improve your code in the long run). And finally, note the index count to move the position along in the array to which you are inserting your lines to.

Getting size and comparing attribute value from ArrayList in other class

I am trying to create a method which creates a result for a athlete in a competition. I have an ArrayList with the athletes in another class and now I want this method to be able to find the size of the ArrayList and also compare one int attribute of every Athlete with the input number. This is what I have so far, Im really stuck. So my quetions to you are: How do I get my for loop to see the size of the ArrayList athletes? and what is a proper way to check whether or not the input has a matching athlete in the ArrayList(I want it to print out if there is no match)? Thank you
public class ResultList {
Scanner scanner = new Scanner(System.in);
ArrayList<Result> resultList = new ArrayList<Result>();
public ResultList() {
ArrayList<Athlete> temp = new AthleteList().getArrayList();
}
void addResult() {
int competetionNumber;
System.out.print("What is the athletes competetionnumber?");
competetionNumber = scanner.nextInt();
scanner.nextInt();
for (int i = 0; i < athletes.size(); i++) {
}
}
}
Other class with the Athlete ArrayList:
public class AthleteList {
ArrayList<Athlete> athletes = new ArrayList<Athlete>();
public AthleteList () {
}
public ArrayList<Athlete> getArrayList() {
return athletes;
}

You should create a variable that points to the AthleteList class. Then you can see that in the addResult method you just get the ArrayList from the AthleteList and call size() on it and iterate over the Athletes and check the completionNumber(You didn't post the Athlete class so I'm assuming there is a completionNumber property). I create a matched variable to hold on to the matched Athlete. After the loop I check to see if one matched and print out the result.
Hope this helps.
public class ResultList
{
Scanner scanner = new Scanner(System.in);
ArrayList<Result> resultList = new ArrayList<Result>();
AthleteList athleteList;
public ResultList()
{
athleteList = new AthleteList();
}
void addResult()
{
int competetionNumber;
System.out.print("What is the athletes competetionnumber?");
competetionNumber = scanner.nextInt();
scanner.nextInt();
Athlete matched = null;
List<Athlete> athletes = athleteList.getArrayList();
for(int i = 0; i < athletes.size(); i++)
{
if(athlete.completionNumber == completionNumber)
{
//you found a match!!
matched = athlete;
}
}
if(matched == null)
{
System.out.println("No Match Found for " + completionNumber);
}
else
{
System.out.println("Found match: " + matched.toString());
}
}
}
NOTE:
Not sure you need the AthleteList class. It's just holding an ArrayList. If that's all that class will ever do then I suggest you just using an ArrayList. It will make your code cleaner.

variable may have not been initialized?

so in the while loop i print some elements of the ArrayList Store. but afterwards when i call it, it says array may have not been initialized.
any thoughts? i'm trying to read a file of lines. each line has at least 8 elements, and i'm sure the array is not empty because i printed from it in the while loop.
?
public class ReaderFile {
public static Scanner input;
public static Scanner input2;
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
int count=0;
ArrayList<Team> store;
ArrayList<Robot> store2;
//Robot robot;
String fileLocation = "Tourney2Teams.csv";
String fileLocation2 = "Tourney1robots.csv";
try{
input = new Scanner(new File(fileLocation)).useDelimiter(",");
}
catch (IOException ioException)
{
System.out.print("PROBLEM");
}
try {
input2 = new Scanner(new File (fileLocation2)).useDelimiter(",");
}
catch (IOException ioException)
{
System.out.print("problem with robot");
}
try{
input.nextLine();
System.out.print("PLEAse\n");
int countt = 0;
while(input.hasNext())
{
//int countt = 0;
int ID = input.nextInt();
String teamName = input.next();
String coachFirst = input.next();
String coachLast = input.next();
String mentorFirst = input.next();
String mentorLast = input.next();
String teamFs = input.next();
String teamSS = input.next();
input.nextLine();
store = new ArrayList<>();
Team team = new Team (teamName, ID, coachFirst, coachLast,mentorFirst,mentorLast,teamFs,teamSS);
store.add(team);
System.out.print("Team Numer"+store.get(0).teamNumber+"\n");
countt = countt+1;
System.out.print("\n"+countt);
}
}
catch (NoSuchElementException statExcemtion)
{
System.out.print("\nAnkosh");
}
String x = store.get(2).teamName;
}
}

store = new ArrayList<>();
This line reinitializes the store at every pass in the while. You probably want to initialize it before the while to accumulate while looping.
It says it was not initialized because for some reason it never executed the while loop (empty input).

It can be uninitialized in two cases:
A NoSuchElementException exception is thrown in your try block, in which case your catch block is executed, and the store is not initialized. I would suggest to either return from the catch block, or move your String x = line inside the try block.
Your loop does zero iterations. In this case the store is also uninitialized. It also looks like a logic error, you probably want your store to be instantiated before the while loop.
I would also suggest to check that the store has at least three elements before accessing element 2.

Entering multiple things in to one array in java

I am quite new to java but have a project i need to complete and am stuck on a certain part.
I want to allow the user to enter a route including, start destination, an end destination, and a number of stops. I have been able to do this, but then i want the user to have the ability of being able to add the same things again, to the same array. without deleting the existing route
here is the code i have so far
import java.util.Scanner;
import java.util.Arrays;
public class main {
public static void main(String[] args){
menu();
}
public static void menu(){
Scanner scanner = new Scanner(System.in);
System.out.println("enter 1 to input a new route");
int option = scanner.nextInt();
if(option==1){
inputRoute();
}
}
public static void inputRoute(){
Scanner scanner = new Scanner(System.in);
System.out.println("Please Enter Starting Destination");
String startDest = scanner.next();
System.out.println("Please Enter End Destination");
String endDest = scanner.next();
System.out.println("Please Enter Number of stops");
int numberOfStops = scanner.nextInt();
String[] stops = new String[numberOfStops];
for(int i = 1; i<=numberOfStops; i++){
System.out.println("Enter Stop" + i);
stops[i-1] = scanner.next();
}
System.out.println(Arrays.toString(stops));
menu();
}
}
however when this runs, if i go back and enter in another route, it will just delete the existing route.
Is there any way of appending the next route to the end of that array or any way of doing this?
thank you

Like crush said. Rather than use a normal array of strings, use an ArrayList<String> object. Or even an ArrayList<String[]> and stash each individual route in there.

First of all you will need to declare the stops array as an instance variable, otherwise you will always be creating a new array whenever you call the method inputRoute().
and then to preserve old entries i can think of two ways-->
--> modify the loop as below...
for(int i = 1; i<=numberOfStops; i++){
System.out.println("Enter Stop" + i);
if(stops!=null) //without the if condition it will also append null in the start
stops[i-1]=stops[i-1]+", "+ scanner.next(); // you can you any separator
else
stops[i-1]=scanner.next();
}
--> or you can ArrayList or any other Collection that provides auto increment

Try declaring stops as a global variable. (right below the class line)
Also I would recommend using an ArrayList, List something on those lines

You can't use an array for this (without constantly re-allocating them) as Arrays are fixed in size once created.
Use an ArrayList though and you can add as many items as you like whenever you like.

The easy (and slightly wrong) solution would be to make your array a static array that is defined outside any method. That will get you going (although you will have to make the array big enought.
Other recommendations:
Capatilize your Main class--avoids confusiong (even moreso if you
don't call it main!)
Make your public static void main method do
this: new Main()
Then get rid of all the other statics.
Use a collection instead of an array.
instead of adding each entry into the array separately (which will make EVERYTHING harder for you), create a second class with 3 fields (start, end, stop) and each time you input another record, "new" an instance of the second class, place the three things into the new instance and place that instance on your collection.
It may seem arbitrary and unnecessary right at this minute, but if you have ANY follow-on work to do on this class these things will make your life easier. If any seems confusing or you want to understand why, feel free to ask in the comments.

I think this will help you.
Main file.
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Main {
public static void main(String[] args){
menu();
}
public static void menu(){
List<Route> routeList = new ArrayList<Route>();
Scanner scanner = new Scanner(System.in);
System.out.println("enter 1 to input a new route");
int option = scanner.nextInt();
if(option==1){
routeList.add(inputRoute());
}
System.out.println("Complete list of routes is "+routeList);
}
public static Route inputRoute(){
Route route = new Route();
Scanner scanner = new Scanner(System.in);
System.out.println("Please enter the name of the route");
String name = scanner.next();
route.setName(name);
System.out.println("Please Enter Starting Destination");
String startDest = scanner.next();
route.setStartLocation(startDest);
System.out.println("Please Enter End Destination");
String endDest = scanner.next();
route.setEndLocation(endDest);
System.out.println("Please Enter Number of stops");
int numberOfStops = scanner.nextInt();
if(numberOfStops > 0){
route.setStopList(new ArrayList<String>());
for(int i = 1; i<=numberOfStops; i++){
System.out.println("Enter Stop" + i);
route.getStopList().add(scanner.next());
}
System.out.println("current entered route is "+route);
menu();
}
return route;
}
}
Route file:
import java.util.List;
public class Route {
String name ;
String startLocation;
String endLocation;
List<String> stopList;
public Route() {
}
public Route(String name, String startLocation, String endLocation, List<String> stopList) {
this.name = name;
this.startLocation = startLocation;
this.endLocation = endLocation;
this.stopList = stopList;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getStartLocation() {
return startLocation;
}
public void setStartLocation(String startLocation) {
this.startLocation = startLocation;
}
public String getEndLocation() {
return endLocation;
}
public void setEndLocation(String endLocation) {
this.endLocation = endLocation;
}
public List<String> getStopList() {
return stopList;
}
public void setStopList(List<String> stopList) {
this.stopList = stopList;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Route route = (Route) o;
if (endLocation != null ? !endLocation.equals(route.endLocation) : route.endLocation != null) return false;
if (name != null ? !name.equals(route.name) : route.name != null) return false;
if (startLocation != null ? !startLocation.equals(route.startLocation) : route.startLocation != null)
return false;
if (stopList != null ? !stopList.equals(route.stopList) : route.stopList != null) return false;
return true;
}
#Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + (startLocation != null ? startLocation.hashCode() : 0);
result = 31 * result + (endLocation != null ? endLocation.hashCode() : 0);
result = 31 * result + (stopList != null ? stopList.hashCode() : 0);
return result;
}
#Override
public String toString() {
return "Route{" +
"name='" + name + '\'' +
", startLocation='" + startLocation + '\'' +
", endLocation='" + endLocation + '\'' +
", stopList=" + stopList +
'}';
}
}