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Issue with scanner in main method vs in constructor java?

SOLVED
I'm having an issue using Scanners nextInt() method in a class constructor.
it works fine if used in a main method like the code below however when doing the same thing in a constructor I get an inputmismatchexception,
what could be the possible issues?
public class QuickTest{
public static void main(String[] args) throws Exception{
java.io.File myFile = new java.io.File("tograph.txt");
java.util.Scanner input = new java.util.Scanner(myFile);
int numberOfPoints = input.nextInt();
String[] myArray = new String[numberOfPoints];
//need to use nextLine once after reading in number of points to get to next line
input.nextLine();
int count = 0;
while(input.hasNext() == true){
myArray[count] = input.nextLine();
count++;
}
input.close();
for(int i = 0; i < myArray.length; i++){
System.out.println(myArray[i]);
}
the class version
public class MyGraph{
//filled with strings from file
String[] points;
java.io.File file;
java.util.Scanner input;
//length of points array
int numPoints;
public MyGraph(String file){
this.file = new java.io.File(file);
this.input = new java.util.Scanner(file);
this.numPoints = this.input.nextInt();
this.points = new String[this.numPoints];
fillGraphArray();
}
//after getting the number of vertices we populate the array with every
//line after those points untill the end
private void fillGraphArray(){
//used once after reading nextInt()
this.input.nextLine();
int count = 0;
while(this.input.hasNext() == true){
points[count] = input.nextLine();
count++;
}
input.close();
}
//test method to be delted later
public String[] getPoints(){
return this.points;
}
//may need a method to close the file
}
When I use the debugger the main method version will get the number of points from the file and then fill the array with a string from each following line in the file however the class version throws the exception

Read integers from file and save two integers per index in a ArrayList

I have research about what I am trying to accomplish. This is my code, and here the main function is to read a file.txt which has integers separated by white spaces and they will be read one by one. However, I want to know... How Can I stored the integers inside a ArrayList, But in each index of the ArrayList there will be two integers instead of one, as usual?
import java.io.File;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;
public class ReadFile {
public static void main(String[] args) {
int[] arr = readFile("address.txt");
System.out.println("The memory block generated is:");
System.out.println(Arrays.toString(arr));
}
// access this method in FIFO
public static int[] readFile(String file) { // this main method
try { // try and catch
File f = new File(file);
#SuppressWarnings("resource")
Scanner r = new Scanner(f); // read the file with scanner
int count = 0; // count for the integers
while(r.hasNextInt()) { // while keep reading
count++;
r.nextInt();
}
int[] array = new int[count];
#SuppressWarnings("resource")
Scanner readAgain = new Scanner(f); // read again
ArrayList<ArrayObjects> blockMem = new ArrayList<>(); // array size * we can use dynamic array
for(int i = 0; i < count; i++) {
// i want to iterate and save them
}
return array;
} catch(Exception fnf) {
System.out.println(fnf.getMessage() + "The file could not be open, try again");
System.exit(0);
}
return null;
} // method closed
}`

Create a new class with two integers.
class TwoIntegers{
int one,two;
TwoIntegers(int data1,int data2){
one = data1;
two = data2;
}
}
Now create an Arraylist of objects of type TwoIntegers
ArrayList<TwoIntegers> blockMem = new ArrayList<TwoIntegers>();
//now you can iterate and insert integers you need
blockMem.add(new TwoIntegers(1,2));
blockMem.add(new TwoIntegers(3,4));

How is using a char array parameter benefits the solution?

The assignment states that there's another class that will call this class. It is similar to betting - you select 12 characters and put them in the array and the program will output a random set of characters. Then it will calculate how many of those matched.
The teacher told me that there should be a parameter of char[] type in the print() method and two in the checked method, but I don't understand the need for them. I could make something similar without his weird choices, but I'm stuck with that. Therefore, I am wondering, if anyone understands the reason for that. It is a method for user input already and it is a method for the computer generated randoms, so I don't see why I have to put a parameter on the other methods. Can't see how that is a logical choice.
Code to solve the assignment:
import java.util.Random;
import java.util.Scanner;
import java.util.Arrays;
public class Tipping
{
char[] ukensRekke;
public Tipping()
{
ukensRekke = new char[12];
}
public void WeekResult(){
String HBU = "HBU";
for(int i = 0; i < ukensRekke.length; i++){
ukensRekke[i] = HBU.charAt((int)(Math.random()*3));
}
}
public char[] getWeekResult(){
return ukensRekke;
}
public void print(char[] tastet){
tastet = new char[12];
for(int i = 0; i < tastet.length; i++){
System.out.print(tastet[i]);
}
}
public char[] register(){
Scanner scan = new Scanner(System.in);
char[] vinnerTall = new char[12];
for(int i = 0; i < vinnerTall.length; i++){
System.out.println("Skriv inn H,B eller U for kamp" + (i+1) + "; ");
vinnerTall[i] =scan.next().charAt(0);
System.out.println(vinnerTall[i]);
}
return vinnerTall;
}
public int check(char[] original, char[] tastet){
original = ukensRekke;
tastet = register();
return tastet.length;
}
}
UPDATE: Hi, so I was somewhat able to solve the problem, but it's still one finishing touch. Here's the part of the code I have problems with, hope someone can help me out.
System.out.println("Klassen Tipping instansieres...");
System.out.println();
System.out.println("Ukens rekke genereres...");
System.out.println();
System.out.println("Brukers rekke registreres.");
tp.register();
System.out.println();
System.out.println("Ukens rekke hentes...");
System.out.println();
System.out.println("Ukens rekke;");
tp.print(tp.getWeekResult());
System.out.println("Brukers rekke;");
tp.print(tp.register());
System.out.println();
System.out.println("Bruker hadde" + tp.check(tp.getWeekResult(),tp.register()) + "riktige tippetanger");
this is the class that I use to make a kinda like sheet, it prints out everything on the screen and takes the user input, but the last two method calls doesn't work, the program just skips it and starts all over again.
and this is the code I use that gets called from:
public void WeekResult(){
String HBU = "HBU";
for(int i = 0; i < ukensRekke.length; i++){
ukensRekke[i] = HBU.charAt((int)(Math.random()*3));
}
}
public char[] getWeekResult(){
return ukensRekke;
}
public void print(char[] tastet){
System.out.print(taste);
}
public char[] register(){
Scanner scan = new Scanner(System.in);
char[] vinnerTall = new char[12];
for(int i = 0; i < vinnerTall.length; i++){
System.out.println("Skriv inn H,B eller U for kamp" + "; ");
vinnerTall[i] = scan.next().charAt(0);
}
return vinnerTall;
}

Your teacher asks you to use a char[] array over a String object simply to use less memory.
Read the answer(s) to this question: How much memory does a string use in Java 8?
One of the answer shows that a String object takes up a minimum of 80 (-8) bytes in memory. In your case, the char array ukensRekke needs only 12 * 2 = 24 bytes. So less memory is used. This is a good advice. You should always keep these efficiency factors in mind to be able to make efficient programs.

Get next run from a text file

I am trying to write a function in Java that returns the next ascending sequence (run) from a txt file, let's say the return type of a function would be ArrayList.
My example file input.txt contains next values: 78123421. So in terms of runs that means the file has 4 runs: |78|1234|2|1|.
What am I trying to reach here is like when I would call this function from main() four times it should print something like
1.run: 78,
2.run: 1234,
3.run: 2,
4.run: 1
or just two calls should print
1.run: 78,
2.run: 1234
I have tryed to solve my problem using BufferedReader/FileReader and RandomAccessFile but no working solution so far, please help :/
So this is what I have so far. The main idea was to use RandomAccessFile and read from input as long as run condition is satisfied. But the reader reads one value more, that is why I use seek() to start reading at the right position when next function call happens. There must be a bug in the code, because it doesn't print all the runs or just an Exception fires.
import java.io.File;
import java.util.ArrayList;
import java.io.RandomAccessFile;
public class GetRunsFromFile
{
static long start = 0;
static long read_len = 0;
public static void main(String[] args) throws Exception
{
File in = new File("C:/Users/henrich/Desktop/Gimp.txt");
RandomAccessFile raf = new RandomAccessFile(in,"r");
ArrayList<Integer> current_run = new ArrayList<Integer>();
for(int i=1;i<=4;i++)
{
current_run = getNextRun(raf);
printArrayList(current_run);
}
raf.close();
}
private static ArrayList<Integer> getNextRun(RandomAccessFile raf) throws Exception
{
int v;
String line;
int val = Integer.MIN_VALUE;
ArrayList<Integer> run = new ArrayList<Integer>();
while((line=raf.readLine())!= null)
{
v = Integer.parseInt(line.trim());
if(v >= val)
{
read_len = raf.getFilePointer() - start;
start = raf.getFilePointer();
run.add(v);
val = v;
}
else
{
raf.seek(raf.getFilePointer() - read_len);
start = raf.getFilePointer();
return run;
}
}
return null;
}
private static void printArrayList(ArrayList<Integer> al)
{
for(int i=0; i<al.size(); i++)
{
System.out.print(al.get(i) + " ");
}
System.out.println();
System.out.println("------");
}
}
For more questions please let me know.
Note: It should work only for ascending runs and files of any length.
Thanks for the support.

There are several ways to do it.
solution 1
For instance call your function with an int and make it return an int refering to the number of the last printed char.
Run Exaple:
after the first run return 2 cause the length of print text is 2
after the second run return 6 cause the length of print text is 4 +2 from last loop... etc.
public int function(int startPoint){
// do stuff here
return lastIndexofPrintChar;
}
then call your function like this
loop{
int result=0;
result= function(x);
}
solution 2
You can also dublicate your file and remove every String you print.

private static void getNextRun()
{
try
{
BufferedReader br = new BufferedReader(new FileReader(new File("C:/Users/henrich/Desktop/Gimp.txt")));
br.skip(skip_lines);
int v;
String line;
int val = Integer.MIN_VALUE;
ArrayList<Integer> al = new ArrayList<Integer>();
while((line=br.readLine())!= null)
{
skip_lines += line.length()+2;
v = Integer.parseInt(line.trim());
if(v >= val)
{
al.add(v);
val = v;
}
else
{
skip_lines -= line.length() + 2;
printArrayList(al);
break;
}
}
br.close();
}
catch (Exception e){System.out.println("EOF");}
}

Error: NoSuchElementException when trying to read values from file to array

Okay. So this is the last HW assignment of the semester, I am leaving out a big part of the program because this is the only thing I can't seem to fix. I am setting up my FileInputStream and using a for loop to read values into the array as I have done in the past without problems. For some reason I am getting this exception and can't figure it out. I have looked at plenty of other threads around this exception but likewise, cant seem to figure it out. Please halp.
Here is the code, it compiles;
import java.util.*;
import java.io.*;
public class CollinDunn_1_10 {
// Declare constants
static final int MAX_EMPLOY = 30;
static final String TAB = "\t";
static final String NL = "\n";
static final double IRA_INVEST = .08;
static final double FEDERAL_WITH = .18;
static final double STATE_WITH = .045;
static final double SAVINGS = .10;
public static void main (String [] args) throws Exception {
// I/O String references
final String INPUT = "CollinDunn_1_10_Input.txt";
final String OUTPUT = "CollinDunn_1_10_Output.txt";
// Declare variables
// One-dimensional array for storing employee names
String [] names = new String [MAX_EMPLOY];
// Two-dimensional array for storing employee pay data
// [0] hours worked [1] pay rate [2] gross pay [3] net pay
// [4] savings amount [5] IRA amount [6] taxs withheld
double [][] payInfo = new double [MAX_EMPLOY][6];
// Set up I/O
FileInputStream inputDataFile = new FileInputStream(INPUT);
Scanner inputFile = new Scanner(inputDataFile);
FileWriter outputDataFile = new FileWriter(OUTPUT);
PrintWriter outputFile = new PrintWriter(outputDataFile);
// Read data from the file
readData(inputFile, payInfo, names);
// Test printing to see if values are stored - REMOVE
for (int i = 0; i < MAX_EMPLOY; i++) {
System.out.print(names[i] + TAB + payInfo[i][0] + TAB + payInfo[i][1]);
}
} // End main
// Method for reading file data into the file.
// Data is sorted as (number of hours) (pay rate) (name)
public static void readData (Scanner inputFile, double [][] payInfo, String [] names) {
for (int i = 0; i < MAX_EMPLOY; i++) {
payInfo [i][0] = inputFile.nextDouble();
payInfo [i][1] = inputFile.nextDouble();
names [i] = inputFile.nextLine();
} // End For
return;
} // End readData
} // End Class
*The fields on the text file are as so:
(hours) (pay) (name)
50.00 10.60 Light Karen L
52.00 10.80 Fagan Bert Todd
62.00 12.24 Antrim Forrest N*
The Exception and stack trace:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextDouble(Scanner.java:2413)
at CollinDunn_1_10.readData(CollinDunn_1_10.java:56)
at CollinDunn_1_10.main(CollinDunn_1_10.java:42)

You're never checking whether there is a value to retrieve before trying to retrieve it (look up Scanner.hasNextDouble). Since your for-loop goes through MAX_EMPLOY iterations, this exception will occur whenever your input file contains less than MAX_EMPLOY lines of data.

You should everytime check if your tables or your file contains right amounts of elements or if they are big enought. Code should look like:
public static void readData (Scanner inputFile, double [][] payInfo, String [] names) {
Integer payInfoLenght = payInfo.lenght;
Integer namesLenght = names.lenght;
if (MAX_EMPLOY > payInfoLenght || MAX_EMPLOY > namesLenght) {
System.out.println("Wrong size of tabels");
} else {
for (int i = 0; i < MAX_EMPLOY; i++) {
if (inputFile.hasNextDouble()) {
payInfo [i][0] = inputFile.nextDouble();
}
if (inputFile.hasNextDouble()) {
payInfo [i][1] = inputFile.nextDouble();
}
if (inputFile.hasNextLine()) {
names [i] = inputFile.nextLine();
}
}
}
}
And you don't need "return;" at the end of this method becouse this method nothing returns. It's "void" method.