Creating a member function /method/, which makes array of primitive data types - int, double, String simultaneously

Question

I have a homework task where I am required to write only 1 method (a member of class MainClass) which creates simultaneously more than one type of array -with only using this method. I tried to create a method that returns the corresponing type but then it can only be done with one type of array (see the commented code /function/). My question is how can I create sort of a templated function which returns all types at once my attemp is below, /but sadly not working/?

   import java.lang.reflect.Array;
import java.sql.SQLOutput;
import java.util.Arrays;

public class MainClass {
    //ще направим отделни методи за класовете
/*public int [] returnArr(){
    int [] ar = new int[10];
    return ar;
}*/
public void createArray(){
    //here I create more than one type of array:
    int []ar = new int[10];
    String[] str  = new String[10];
    double [] dbl  = new double[10];
}
}
class Test{
    public static void main(String[] args) {
        MainClass mcl = new MainClass();
       /*int [] ia = mcl.returnArr();
        for (int i = 0;i<10;i++){
            Arrays.fill(ia,0,9,8);
        }*/
       mcl.createArray();
       //here the ar[] array is not accessible
        Arrays.fill(ar,0,9,0);
       for (int i:ar){
           System.out.println(i);
       }
    }
}

Answer 1

I hope you are practicing OOPs. In Java , its not possible for a method to return multiple types. You have mentioned, you need to create multiple types of arrays using a single method. You can go by 2 methods here.

1. The Object oriented way - use the instance variables & initialize them in one method. It would be something like below

   public class MainClass {

    private int[] intArray; private String[] strArray; private double[] dblArray; public void createArray() { this.intArray = new int[10]; this.strArray = new String[10]; this.dblArray = new double[10]; } 

   }

And then you can use some getter methods to access the arrays.

2. Return array of arrays - You can return multiple values as a composite type array. For example array of java.lang.Object . Since Object is the parent class of everything in Java, an array of Object can hold any types. then your method would look like

  public Object[] createArray() { int[] intArray = new int[10]; String[] strArray = new String[10]; double[] dblArray = new double[10]; Object[] returnArray = new Object[] { this.intArray, this.strArray, this.dblArray }; return returnArray; } 

Now in the Object array that is returned

Object[] arrays = mcl.createArray();

// arrays[0] is an integer array, arrays[1] is string array and so on.
int[] arr = arrays[0];

Now you can use the arrays in the manner you need. Hope you are clear on the concept.