Easy dynamic object names in java?

[LeperousDust]

I've got a loop running creating objects, but i don't know how to give the objects dynamic names such as "intCell(i)" in this case where i would be the loop counter. Surely there is any easy way, but my googling is weak and i'm not entirley sure what i should be looking for.

public static IntList array2intList(int[] i) {
       for (int j=0; j<i.length; j++) {
		IntCell intCell(i) = new IntCell(null, i[j], null);
	}
       return null;
    }

 

[LeperousDust]

Right i had it as an IntCell array, becuase that was the only way i could think of doing it, and i got told by my tutor thats "over complicating thins"? I'm making a doubly linked list of objects, so they don't need to be held in an array technically. But i don't know how else i'd do this, i wish i'd just asked him now (i just thought at the time it would be fairly simple...)

List and/or map maybe what i want; i will have a play

 

[LeperousDust]

class IntList {
    final static int PLAIN    = 0;
    final static int EXTENDED = 1;
	
    IntCell first;
    IntCell last;

    IntList(IntCell f, IntCell l) {
       first = f;
       last  = l;
    }


    // Transform an array of integers into
    // a doubly-linked list of integers.
    public static IntList array2intList(int[] i) {
       for (int j=0; j<i.length; j++) {
		IntCell  = new IntCell(null, i[j], null);
	}
       return null;
    }

****More stuff should be here that is irrelevant i've just taken out***

    // Pretty Print a doubly-linked list.
    // Views: * PLAIN, e.g. [ 3, 4, 5 ]
    //        * EXTENDED, includes all references 
    public void printIntList(int view) {
    	if (view == EXTENDED) {
			System.out.print("FIRST: ");
			System.out.println(first);
			System.out.print("LAST: ");
			System.out.println(last);
			System.out.println();
		}
    	IntCell next = this.first;
    	boolean start = true;
		if (view == PLAIN) { 
			System.out.print("[ ");
		}
		
		while (next != null) {
			if (view == EXTENDED) {
				next.printIntCell();
			} else {
                if (!start) {
                    System.out.print(", ");
                }
				System.out.print(next.contents);
			}			
			start = false;
			next  = next.successor; 
       	}
		
		if (view == PLAIN) {
		    System.out.println(" ]");
		}
    }
}



package LinkedLists;
class IntCell {
    int     contents;
    IntCell predecessor;
    IntCell successor;

    IntCell(int i) {
       contents = i;
       predecessor = null;
       successor = null;
    }
    
    IntCell(IntCell p, int i, IntCell s) {
       contents = i;
       predecessor = p;
       successor = s;
    }
    
    public void printIntCell() {
	    System.out.print(contents);    
	    System.out.print(" : ( ");
	    
	    System.out.print(predecessor);    
	    System.out.print(" ) <---p--- ( ");
	    System.out.print(this);    
	    System.out.print(" ) ---s---> ( ");	    
		System.out.print(successor);
		
	    System.out.println(" )");  
	}
}

 

[LeperousDust]

sorry double post

 

[LeperousDust]

Right i think i've got it but i'm getting a null pointer exception when i try and pass it an array of intergers but i can't see why

public static IntList array2intList(int[] i) {
    	if (i.length == 0) {
            return new IntList(null, null);
        }
        else {
            IntCell first       = new IntCell(i[0]);
            IntCell current = first;
           
            for (int counter = 1; counter < i.length; counter++) {
                 IntCell next = new IntCell(current, i[counter], null);
                 current.successor = next;
                 next.predecessor  = current;
                 current = next;
            }
            return new IntList(first, current);
        }
    }

Any clues?

 

[LeperousDust]

Hmmm, i thought it should work, wtf, why do i seem to keep having problems!

Thats what i should be doing thought right, instead of using arrays? As the point in a doubly (and single) linked list is you can't straight access any cell (unlike an array).

 

[LeperousDust]

hmmm it works now, not quite sure what was happening there and then but i may have corrupted objects when i was messing around with another method and the objects weren't being flushed from run to run i guess?

 

[LeperousDust]

What i don't understand properly about these linked lists even though i have got it to work is how they know they're related to each other? I mean none of the objects have names, but i've pointed them to the successor and predecessor but then i make new objects with the same name? Are the references not by name and instead actual memory references the name just being a convenience? I'm slightly confused by this aspect...

 

[LeperousDust]

It is really cool, i've been playing around for the last hour now and i think i'm getting to grips with the whole concept properly, confused me a lot to begin with I've not thought of using recursive methods actually, thats an idea, i've just been using while or for loops to traverse them... We were told recursive things can be quite inefficient? Last semester we start Haskell from scratch to put us all on a level playing field, now that was weird, but its recursiveness was pretty cool, but now theyre telling us not to think like that, which is a bit strange. Are there any good java resources i should look at? I've got myself a pretty good cheat sheet or two which is nice, and learning how to use content assist in eclipse pretty efficiently, i just wonder if theres any thriving communities for beginners/novices like me to talk?