Accessing variable in Main method from other class

Question

I have two classes:

public class node {
  static LinkedList<Integer> nodes = new LinkedList<Integer>();
  public boolean visited;

  public static void Main (String args []) {
    System.out.println("Number of nodes in network");
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();

    for (int i=1;i<=n;i++){
      nodes.add(i);
    }

    System.out.println(nodes);
  }

and another class

public class AdjacencyList {
  private int n;
  private int density;

I want to access int n from Mainmethod and assign its value to private int n in AdjacencyList class. I tried node.n (class.variable) format in a method where I can assign values but its not working out. Can anybody please help me with this?

"n" have to be public & static, or private & static bud, you have to have method to Get n :) — Tomas Bisciak
– Tomas Bisciak, Commented Nov 24, 2013 at 19:14
How exactly do you plan to use this n from main and where do you want to create the AjacentList, in the main? — Paul Samsotha
– Paul Samsotha, Commented Nov 24, 2013 at 19:19

subash · Accepted Answer · 2013-11-24 19:14:40Z

7

change to

public static int n;

then you can access anywhere like this..

AdjacencyList.n

answered Nov 24, 2013 at 19:14

subash

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4 Comments

iberbeu Over a year ago

This is actually a pretty bad solution. Variables shouldn't be public. Any way, if you want to do that ´AdjacencyList´ must be static

Tomas Bisciak Over a year ago

@iberbeu When its a small program why not.Not like its going to confuse anyone.Bud he shoud pick another name for that variable this might be confusing later on.

Gaurav K. Over a year ago

I would change the name of variable. It has already started confusing me.. @iberbeu May I know why variables should not be public?

iberbeu Over a year ago

As a common pattern variables should be declared as private. You then will provide getter and setter for getting acces to it. If you do it so, you ensure that your class is allways managing the way its fields are changing. So normally, declaring attributes as public is a bad thing. Sometimes it is needed though. Any way I don't recomend it. The question could be: why should a variable be private?

Melquiades · Accepted Answer · 2013-11-24 20:00:38Z

3

Simply,

public class AdjacencyList {
    private int n;
    private int density;

    //method to get value of n
    public int getN() { return this.n; }

    //method to set n to new value
    public void setN(final int n) { this.n = n; }

Then, in your main(), you can do this:

AdjacencyList myList = new AdjacencyList();

//set n to any value, here 10
myList.setN(10);

//get n's current value
int currentN = myList.getN();

All this is basic java stuff, please go through the docs again, especially here and here.

answered Nov 24, 2013 at 20:00

Melquiades

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Comments

igr · Accepted Answer · 2013-11-24 19:15:48Z

0

You can't. Local variables (variables defined inside functions) have scope limited to this function (here Main, note: it is practice to start with lowercase character for function names).

If you want some variable to be accessed from outside, it needs to be class variable and that you declare functions to access it ( setN / getN or similar...)

Also, as function is static, variable also needs to be static.

Hope it helps

answered Nov 24, 2013 at 19:15

igr

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Comments

Dave Hulse · Accepted Answer · 2013-11-24 19:17:33Z

0

You can do that or you can create a new instance of AdjacencyList and set n in the constructor. Then access n with a get() function.

answered Nov 24, 2013 at 19:17

Dave Hulse

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Comments

quez · Accepted Answer · 2013-11-24 19:24:06Z

0

Add to the second class public setter for n, then create an instance of AjacencyList in main and call the setter.

answered Nov 24, 2013 at 19:24

quez

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