Question

import java.util.Arrays;
import java.util.*;

class Main {
public static void main(String[] args) {

}
  }

 class List {


private static final int NUMINTS = 10;
public List(int numints) {

    int list[];
    list = new int[NUMINTS];

}

public void fillWithRandom(int list[]) {
 Random r;
 r = new Random();

 int i;

 for(i=0; i < NUMINTS ; i++)
     list[i] = r.nextInt();
} 

public void print(int list[]) {
    int i;
    System.out.println("before sort():");
    for(i=0 ; i < NUMINTS; i++)
        System.out.println(list[i]);

    Arrays.sort(list, 0, NUMINTS);
    System.out.println("--------");
    System.out.println("after sort():");
    for (i = 0 ; i < NUMINTS; i++)
        System.out.println(list[i]);
}
   }

I want to create an array of random numbers. I am not quite sure how to implement the methods from my class List into the Main class. I want main to create the array and then print it out.

Answer 1

One problem in your code is that you are not using the argument passed,

    public List(int numints) { // numints never used, hence useless
       int list[];
       list = new int[NUMINTS];  // list is a local variable. It has no scope outside this 
                                 // method and the method also doesn't have any side-effect    
    }

Now, come to the point, how you can call methods of List class in your Main class’s main() method.

public static void main(String[] args) {
    List list = new List(10);
    int[] intArr = new intArr[10];

    list.fillWithRandom(intArr);
    list.print(intArr);
}

Few suggestions,

1. Its better to declare array type like this int[] arr; instead of int arr[]
2. If you must use 2 classes, then it seems you should have a int[] intArr; in your List class. So, you need not pass intArr back or forth
3. Initialise the array using the arguments received, not with the NUMINTS