Creating instances of static nested class within that

Question

This is related to Declaring an instance of a class inside that class

Why the static inner class Node allows the new Node[R] field within the class, and why the infinite recursion is not happening here?

public class TrieST<Value> {
   private static final int R = 256;        // extended ASCII


   private Node root;      // root of trie
   private int N;          // number of keys in trie

  // R-way trie node
  private static class Node {
    private Object val;
    private Node[] next = new Node[R];
  }
...
}

x = new Node(); // is fine within the containing class, but new Node[R] inside static nested Node class is not clear.

Where do you see a infinite recursion and why should it happen? — SomeJavaGuy
– SomeJavaGuy, Commented Jul 23, 2015 at 6:15
new Node[] just initializes the array. It doesn't create R Node objects. — Codebender
– Codebender, Commented Jul 23, 2015 at 6:16
While creating a instance of nested class via new Node[R]. I the reason is it's being static then why the construction is allowed via new? — unknown_boundaries
– unknown_boundaries, Commented Jul 23, 2015 at 6:17
@Prakhar you don´t create a new instance of a node, you just create a Array of the size 256, with 256 elements beeing null. There is no way where a recursion could happen. — SomeJavaGuy
– SomeJavaGuy, Commented Jul 23, 2015 at 6:18
Side note: "extended ASCII" is not a precise definition of an encoding. If you're trying to represent a specific encoding, you should state what it is. — Jon Skeet
– Jon Skeet, Commented Jul 23, 2015 at 6:21

Seelenvirtuose · Accepted Answer · 2015-07-23 06:17:49Z

3

The line

private Node[] next = new Node[R];

declares and initializes the field next which is an array reference (you should read Node[] as "Node array"). The expression new Node[R] does not create any node, it creates an array of nodes. So there is no recursion.

If you had a field such as

private Node someNode = new Node();

then indeed you would have a recursion because each node would create another node that creates a next one, and so on.

answered Jul 23, 2015 at 6:17

Seelenvirtuose

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