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How to I call a method to create arrays from another class?

So I have this code in the main class
public class OneDArrays
{
public static int[] create (int size)
{
int[] a1 = new int[size];
for (int i = 0; i < size; i++)
{
a1[i] = i*2+1;
}
return a1;
}
public int sumSome (int[] b1, int howmany)
{
int sum = 0;
if (howmany <= b1.length)
{
for (int i = 0; i < howmany; i++)
{
sum = sum + b1[i];
}
}
else
{
sum = -1;
}
return sum;
}
public int[] grow (int[] c1, int extra)
{
int[] newArray = new int[c1.length+extra];
for (int i = 0; i < newArray.length; i++)
{
while (i <= c1.length)
{
newArray[i] = c1[i];
i++;
}
newArray[i] = 0;
}
return newArray;
}
public void print (int[] d1)
{
for (int i = 0; i < d1.length; i++)
{
System.out.println (d1[i] + ", ");
}
}
}
And then I have my tester class,
public class OneDArraysTester
{
public static void main (String[] args)
{
int[] test1;
test1.create (5);
}
}
How do retrieve the method from the first class? I get the error that "create" is an undeclared method. If the "create" method were a constructer, I know I could just type create test1 = new create (5) but I don't see a way to turn it in to a constructer, so what's the way of doing that but for a method?

You invoke a static method with the classname. Literally className.methodName. Like,
int[] test1 = OneDArrays.create(5);

You have made a class named OneDArrays so you can call it's methods by creating an instance or object of that class.
like this :
OneDArrays ObjectOfClass = new OneDArrays();
int test1[] = ObjectOfClass.create(5);
similarly you can also call other methods of that class by accessing methods of this newly created object ObjectOfClass.
like :
sumOfArray = ObjectOfClass.sumSome(test1,3);
int biggerTest1[] = ObjectOfClass.grow(test1,10);
If you want to make create method works as a constructor than you can but you cannot return value from a constructor so you cannot return your array from that constructor.

Since you have declared the create method as static, #ElliotFrisch is the best way. But, it is not always a good idea to make methods static. So another way to achieve what you want would be to make the create method non-static.
public int[] create (int size){/*Method Body*/};
And then create an object of the OneDArray class to access the method.
OneDArrays oneDArrays = new OneDArrays();
int[] test1 = oneDArrays.create(5);
or,
int[] test1 = new OneDArrays().create(5);

Array Method issue

having a problem with my java program. I am a newbie to Java and just can't figure out what is exactly the issue with it. In short I've declared an array and a variable in main, I've created my method call and would like my array be passed into my method with the variable. I would then like the method to take my array and count the number of times my variable "8" occurs, get rid of the 8 out of the array and return a new smaller array back to main. Here is my code below. I feel as if I am just missing one block code any suggestions?
public class Harrison7b
{
public static void main(String [] args)
{
int[] arrayA = {2,4,8,19,32,17,17,18,25,17,8,3,4,8};
int varB = 8;
// Call with the array and variable you need to find.
int[] result = newSmallerArray(arrayA, varB);
for(int x = 0; x < arrayA.length; x++)
{
System.out.print(arrayA[x] + " ");
}
}
public static int[] newSmallerArray( int[] arrayA, int varB)
{
int count = 0;
for(int x = 0; x < arrayA.length; x++)
{
if(arrayA[x] == varB)
{
count++;
}
}
int [] arrayX = new int[arrayA.length - count];
for(int B = 0; B < arrayA.length; B++)
{
if(arrayA[B] != varB)
{
}
}
return arrayX;
}
}

you do not actually need to return the array because when you pass an array to a method you also pass its memory address meaning its the same address that you change so, it will also change the arraysA of main method because you are just changing the values of the same memory adress
import java.util.*;
public class Help
{
public static void main(String[] args)
{
ArrayList<Integer> arraysA = new ArrayList<Integer>();
arraysA.add(Integer.valueOf(2));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(19));
arraysA.add(Integer.valueOf(32));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(18));
arraysA.add(Integer.valueOf(25));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(3));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
int varB=8;
newSmallerArray(arraysA,varB);
for(Integer i:arraysA)
{
System.out.println(i);
}
}
public static void newSmallerArray(ArrayList<Integer> arraysA,int varB)
{
for(int i=0;i<arraysA.size();++i)
{
if(Integer.valueOf(arraysA.get(i))==varB)
{
arraysA.remove(i);
}
}
}
}

Try this code it will not require for loop:
List<Integer> list = new ArrayList<Integer>(Arrays.asList(arrayA));
list.removeAll(Arrays.asList(8));
arrayA = list.toArray(array);

How to read copy the array with the array from another class? [In loading file]

I want to create a game and I need to read file from the notepad
when I use my loadfile.java alone, it work very well. Then, I would like to copy my data into datafile.java as it will be easier for me to do the fighting scene. However, I can't copy the array in my loadfile.java to the datafile.java and I don't understand why.
import javax.swing.*;
import java.io.*;
import java.util.Scanner;
public class loadfile
{
static String filename = "Save.txt";
static int size = 4;
static int s;
static int[] number;
static String[] line;
private static void load() throws IOException
{
BufferedReader reader = new BufferedReader(new FileReader(filename));
while (reader.readLine()!= null)
{
size++;
}
size -= 4;
reader.close();
line = new String[size];
number = new int[size];
BufferedReader reader2 = new BufferedReader(new FileReader(filename));
for (int i = 0; i < size; i++)
{
line[i] = reader2.readLine();
}
reader2.close();
for (int i = 4; i < size; i++)
{
number[i] = Integer.parseInt(line[i]);
}
}
public static String[] getData()
{
return line;
}
public static int[] getNumber()
{
s = size - 4;
int[] num = new int[s];
for (int i = 0; i < s; i++)
{
num[i] = number[i+4];
}
return num;
}
public static int getDataSize()
{
return size;
}
public static int getNumberSize()
{
return size - 4;
}
This is my loadfile.java
I use the file with 4 names and 9 * n int in the notepad as I want to check whether I have the character first before I read the file. However, before I can handle this problem, I got another problem that I can't copy the array into my datafile.java
The datafile.java is separate with two constructor. One is for Starting the game and one is for loading the data. The constructor with the (int num) is the problem I have. First, I would like to show the java first:
import java.util.Arrays;
import java.io.*;
public class datafile
{
private static String[] data;
private static int[] number;
private static String[] name;
private static int[] a, d, s;
private static int[] hp, maxhp;
private static int[] mp, maxmp;
private static int[] lv, exp;
public datafile()
{
initialization();
name[0] = "Pet";
a[0] = 100;
d[0] = 100;
s[0] = 100;
hp[0] = 500;
mp[0] = 500;
maxhp[0] = 500;
maxmp[0] = 500;
exp[0] = 100;
lv[0] = 1;
}
public datafile(int num) throws IOException
{
initialization();
loadfile l = new loadfile();
for (int i = 0; i < l.getNumberSize(); i++)
{
number[i] = l.getNumber()[i];
}
for (int i = 0; i < l.getDataSize(); i++)
{
data[i] = l.getData()[i];
}
for(int i = 0; i < 4; i++)
{
name[i] = data[i];
}
for(int i = 0; i < 4; i++)
{
a[i] = number[1+(i*9)];
d[i] = number[2+(i*9)];
s[i] = number[3+(i*9)];
hp[i] = number[4+(i*9)];
mp[i] = number[5+(i*9)];
maxhp[i] = number[6+(i*9)];
maxmp[i] = number[7+(i*9)];
lv[i] = number[8+(i*9)];
exp[i] = number[9+(i*9)];
}
}
public static String getName(int n)
{
return name[n];
}
public static int getAttack(int n)
{
return a[n];
}
public static int getDefense(int n)
{
return d[n];
}
public void initialization()
{
name = new String[3];
a = new int[3];
d = new int[3];
s = new int[3];
hp = new int[3];
mp = new int[3];
maxhp = new int[3];
maxmp = new int[3];
lv = new int[3];
exp = new int[3];
}
public static void main (String[] args) throws IOException
{
new datafile(1);
}
}
When I run the program, the debugging state this line
data[i] = l.getData()[i];
as an error
I don't know what wrong with this line and I tried so many different ways to change the way the copy the method. However, it didn't work
The error says this:
Exception in thread "main" java.lang.NullPointerException
at datafile.<init>(datafile.java:38)
at datafile.main(datafile.java:92)
I hope you guys can help me with this problem because I don't want to fail with my first work

in your datafile(int num)
you call
loadfile l = new loadfile();
but you never call the load() method on you loadfile
l.load();

Edit: my bad, I didn't see your initialization method, but regardless, I'm going to stick with my recommendation that you radically change your program design. Your code consists of a kludge -- you've got many strangely named static array variables as some kind of data repository, and this suggests that injecting a little object-oriented design could go a long way towards creating classes that are much easier to debug, maintain and enhance:
First I recommend that you get rid of all of the parallel arrays and instead create a class, or likely classes, to hold the fields that need to be bound together and create an ArrayList of items of this class.
For example
public class Creature {
private String name;
private int attack;
private int defense;
// constructors here
// getters and setters...
}
And elsewhere:
private List<Creature> creatureList = new ArrayList<>();
Note that the Creature class, the repository for some of your data, should not be calling or even have knowledge of the code that loads the data, but rather it should be the other way around. The class that loads data should create MyData objects that can then be placed within the myDataList ArrayList via its add(...) method.
As a side recommendation, to help us now and to help yourself in the future, please edit your code and change your variable names to conform with Java naming conventions: class names all start with an upper-case letter and method/variable names with a lower-case letter.

Array won't replace multiples of 2

I want to replace all multiples of 2 in my array with the value 0 and I felt as though this code did this but 4,6 and 8 stay the same in the output.
Am I doing something stupidly wrong?
public static void markOfMultiples(int[]listOfNumbers, int number)
{
for(int i = 0; i<listOfNumbers.length; i++)
{
if (listOfNumbers[i]%number == 0)
{
listOfNumbers[i] = 0;
}
}
}

In mycase your method was working fine,It solely depends how you are invoking your method
You should invoke your method like
public static void main(String[] args)
{
int num[]={2,4,6,11,13,8};
markOfMultiples(num,2);
}
Your method remains the same
public static void markOfMultiples(int[]listOfNumbers, int number)
{
for(int i = 0; i<listOfNumbers.length; i++)
{
if (listOfNumbers[i]%number == 0)
{
listOfNumbers[i] = 0;
}
System.out.println(listOfNumbers[i]);//added by me to track what's going on
}
and its working fine!

Beginner: Assigning values to arrays in Java

I am attempting to write a simple Genetic Algorithm in Java after reading a book on Machine Learning and have stumbled on the basics. I'm out of practice with Java so I'm probably missing something extremely simple.
Individual
public class Individual {
int n;
int[] genes = new int[500];
int fitnessValue;
public int getFitnessValue() {
return fitnessValue;
}
public void setFitnessValue(int fitnessValue) {
this.fitnessValue = fitnessValue;
}
public int[] getGenes() {
return genes;
}
public void setGenes(int index, int gene) {
this.genes[index] = gene;
}
public int getN() {
return n;
}
public void setN(int n) {
this.n = n;
}
// Constructor
public Individual() {
}
}
Population
import java.util.Random;
public class Population {
public Population() {
}
public static void main(String[] args) {
Random rand = new Random();
int p = rand.nextInt(10);
int n = rand.nextInt(10);
Individual pop[] = new Individual[p];
System.out.println("P is: " + p + "\nN is: " + n);
for(int j = 0; j <= p; j++) {
for(int i = 0; i <= n; i++) {
pop[j].genes[i] = rand.nextInt(2);
}
}
}
public void addPopulation() {
}
}
The aim of this code is to populate the Population and the Genes with a random number. Could someone please take a look at my code to see where I'm going wrong?

before
pop[j].genes[i] = rand.nextInt(2);
add
pop[j] = new Individual();
the elements of the array are null.

I believe you need to initialize pop[j] before doing pop[j].genes[i] = rand.nextInt();
Individual pop[] = new Individual[p];
This just initializes the array, not the individual elements. Try to put pop[j] = new Individual() between your two loops.

What they said...
Also, do you mean to call your setGenes method, or do you just want to directly access the gene array.

From what I understand of your code I think you need to do this:
for(int j = 0; j <= p; j++) {
pop[j] = new Individual();
for(int i = 0; i <= n; i++) {
pop[j].setGenes(i, rand.nextInt(2));
}
}