Java recursion: follow the link

Question

I understand that this is a hotly debated, controversial topic for Java programmers, but I believe that my problem is somewhat unique. My REQUIRES algorithm follows the link. I assign virtual coordinates (x, y) clockwise / counterclockwise for a common tree (i.e. N-children). It just means that I count (and mark) the tree nodes that I visit when I find them.

/**
 * Generates a "pre-ordered" list of the nodes contained in this object subtree
 * Note: This is counterclockwise pre-order traversal
 * 
 * @param clockwise set to true for clockwise traversal and false for counterclockwise traversal
 * 
 * @return Iterator<Tree> list iterator
 */
public Iterator<Tree> PreOrder(boolean clockwise)
{
    LinkedList<Tree> list = new LinkedList<Tree>();
    if(!clockwise)
        PreOCC(this, list);
    else
        PreO(this,list);
    count = 0;
    return list.iterator();
}
private void PreOCC(Tree rt, LinkedList<Tree> list)
{
    list.add(rt);
    rt.setVirtual_y(count);
    count++;
    Iterator<Tree> ci = rt.ChildrenIterator();
    while(ci.hasNext())
        PreOCC(ci.next(), list);      
}
private void PreO(Tree rt, LinkedList<Tree> list, int count)
{
    list.add(rt);
    rt.setX_vcoordinate(count);
    Iterator<Tree> ci = rt.ReverseChildrenIterator();
    while(ci.hasNext())
        PreO(ci.next(), list, ++count);
}

Here I generate the tree structure:

Tree root = new Tree(new Integer(0));
root.addChild(new Tree(new Integer(1), root));
root.addChild(new Tree(new Integer(2), root));
root.addChild(new Tree(new Integer(3), root));
Iterator<Tree> ci = root.ChildrenIterator();
ci.next();
Tree select = ci.next();
select.addChild(new Tree(new Integer(4), select));
select.addChild(new Tree(new Integer(5), select));

And here is my conclusion, when I print the order of the nodes and the coordinates that it assigns to the corresponding node.

0 3 2 5 4 1
0 1 2 3 4 3

0 1 2 4 5 3
0 1 2 3 4 3

. x-. y-.

, : 0 1 2 3 4 5

EDIT 1: , , , .

Iterator<Tree> pre = root.PreOrder(true);
System.out.println("              \t");
while(pre.hasNext())
    System.out.print(pre.next() + "\t");

pre = root.PreOrder(true);
System.out.println();
System.out.println("x-coordinates:\t");
while(pre.hasNext())
System.out.print(pre.next().getVirtual_x() + "\t");

System.out.println();
System.out.println();

Iterator<Tree> preCC = root.PreOrder(false);
System.out.println("              \t");
while(preCC.hasNext())
    System.out.print(preCC.next() + "\t");

preCC = root.PreOrder(false);
System.out.println();
System.out.println("x-coordinates:\t");
while(preCC.hasNext())
System.out.print(preCC.next().getVirtual_y() + "\t");

, x, y. . y- .

- T ( 0 n - 1), x- .

T ( 0 n - 1), y- .

Answer 1

Java , - , . , -, , , .

" Java":

"... Java - - ..."

, .

, , Java

, . . , .

Answer 2

, Java:

class Pointer {
    private Object ptr;
    public Pointer(Object v)  { set(v);  }
    public void set(Object v) { ptr = v; }
    public Object get()       { return ptr; }
}

:

public void swap(Pointer a, Pointer b) {
    Object tmp = a.get();
    a.set(b.get());
    b.set(tmp);
}

:

public static void main(String[] args) {
    Integer one = 1; 
    Integer two = 2;
    Pointer pone; pone.set(one);
    Pointer ptwo; ptwo.set(two);
    swap(pone, ptwo);
    System.out.println((Integer) pone.get());
    System.out.println((Integer) ptwo.get());
}

, , , , , Java .

Answer 3

You do not need to follow the link, you need a function with side effects. Passing by reference will be one way to achieve this; Using a modified object as an argument to a function will be different.

private void PreO(Tree rt, LinkedList<Tree> list, int[] count)
{
    list.add(rt);
    rt.setX_vcoordinate(count[0]);
    Iterator<Tree> ci = rt.ReverseChildrenIterator();
    while(ci.hasNext()) {
        ++count[0];
        PreO(ci.next(), list, count);
    }
}