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Fixing bugs found when implementing Bidirectional Iterator unit tests.

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-Fixed: AbstractList/ImmutableList/ArraySet/ArrayMap skip/back implementation was causing crashes and didn't update the last returned value.
-Fixed: ArraySet/ArrayMap previous was not subtracting before returning value.
-Fixed: BidirectionalIterator back was calling the object variant instead of the TypeSpecific Variant.
-Fixed: TreeSets/Maps Iterator now fully supports backwards Iterating.
-Added: Specialized skip/back function to improve speed in ImmutableHashSet/LinkedHashSet/CustomLinkedHashSet
This commit is contained in:
Speiger
2022-06-04 21:05:31 +02:00
parent c1862e6b05
commit 8b5e5a75c1
18 changed files with 502 additions and 175 deletions
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src/builder/resources/speiger/assets/collections/templates/sets/AVLTreeSet.template
+40 -16
View File
@@ -1298,6 +1298,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
boolean unboundForwardFence;
boolean unboundBackwardFence;
@@ -1307,6 +1308,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public AscendingSubSetIterator(Entry KEY_GENERIC_TYPE first, Entry KEY_GENERIC_TYPE forwardFence, Entry KEY_GENERIC_TYPE backwardFence)
{
next = first;
previous = first == null ? null : first.previous();
this.forwardFence = forwardFence == null ? EMPTY_KEY_VALUE : forwardFence.key;
this.backwardFence = backwardFence == null ? EMPTY_KEY_VALUE : backwardFence.key;
unboundForwardFence = forwardFence == null;
@@ -1322,6 +1324,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.next();
forwards = true;
@@ -1330,15 +1333,16 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null && (unboundBackwardFence || next.key != backwardFence);
return previous != null && (unboundBackwardFence || previous.key != backwardFence);
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.previous();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.previous();
forwards = false;
return result;
}
@@ -1346,6 +1350,8 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(previous == lastReturned) previous = previous.previous();
if(next == lastReturned) next = next.next();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
set.removeNode(lastReturned);
lastReturned = null;
@@ -1356,6 +1362,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
boolean unboundForwardFence;
boolean unboundBackwardFence;
@@ -1365,6 +1372,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public DescendingSubSetIterator(Entry KEY_GENERIC_TYPE first, Entry KEY_GENERIC_TYPE forwardFence, Entry KEY_GENERIC_TYPE backwardFence)
{
next = first;
previous = first == null ? null : first.next();
this.forwardFence = forwardFence == null ? EMPTY_KEY_VALUE : forwardFence.key;
this.backwardFence = backwardFence == null ? EMPTY_KEY_VALUE : backwardFence.key;
unboundForwardFence = forwardFence == null;
@@ -1380,6 +1388,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.previous();
forwards = false;
@@ -1388,15 +1397,16 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null && (unboundBackwardFence || next.key != backwardFence);
return previous != null && (unboundBackwardFence || previous.key != backwardFence);
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.next();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.next();
forwards = true;
return result;
}
@@ -1404,6 +1414,8 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(previous == lastReturned) previous = previous.next();
if(next == lastReturned) next = next.previous();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
set.removeNode(lastReturned);
lastReturned = null;
@@ -1415,11 +1427,13 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
public AscendingSetIterator(Entry KEY_GENERIC_TYPE first)
{
next = first;
previous = first == null ? null : first.previous();
}
@Override
@@ -1431,6 +1445,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.next();
forwards = true;
@@ -1439,15 +1454,16 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null;
return previous != null;
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.previous();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.previous();
forwards = false;
return result;
}
@@ -1455,6 +1471,8 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(lastReturned == previous) previous = previous.previous();
if(lastReturned == next) next = next.next();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
removeNode(lastReturned);
lastReturned = null;
@@ -1465,11 +1483,13 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
public DescendingSetIterator(Entry KEY_GENERIC_TYPE first)
{
next = first;
previous = first == null ? null : first.next();
}
@Override
@@ -1481,6 +1501,7 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.previous();
forwards = false;
@@ -1489,15 +1510,16 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null;
return previous != null;
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.next();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.next();
forwards = true;
return result;
}
@@ -1505,6 +1527,8 @@ public class AVL_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(lastReturned == previous) previous = previous.next();
if(lastReturned == next) next = next.previous();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
removeNode(lastReturned);
lastReturned = null;
src/builder/resources/speiger/assets/collections/templates/sets/ArraySet.template
+5 -3
View File
@@ -924,8 +924,8 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = index;
return data[index--];
--index;
return data[(lastReturned = index)];
}
@Override
@@ -964,8 +964,9 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
@Override
public int skip(int amount) {
if(amount < 0) throw new IllegalStateException("Negative Numbers are not allowed");
int steps = Math.min(amount, (size() - 1) - index);
int steps = Math.min(amount, size() - index);
index += steps;
if(steps > 0) lastReturned = Math.min(index-1, size()-1);
return steps;
}
@@ -974,6 +975,7 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
if(amount < 0) throw new IllegalStateException("Negative Numbers are not allowed");
int steps = Math.min(amount, index);
index -= steps;
if(steps > 0) lastReturned = Math.min(index, size()-1);
return steps;
}
}
src/builder/resources/speiger/assets/collections/templates/sets/ImmutableOpenHashSet.template
+24 -4
View File
@@ -502,6 +502,28 @@ public class IMMUTABLE_HASH_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERI
}
}
@Override
public int skip(int amount) {
int result = 0;
while(next != -1 && result != amount) {
current = previous = next;
next = (int)(links[current]);
result++;
}
return result;
}
@Override
public int back(int amount) {
int result = 0;
while(previous != -1 && result != amount) {
current = next = previous;
previous = (int)(links[current] >> 32);
result++;
}
return result;
}
@Override
public boolean hasNext() {
return next != -1;
@@ -530,9 +552,8 @@ public class IMMUTABLE_HASH_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERI
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
current = previous;
current = next = previous;
previous = (int)(links[current] >> 32);
next = current;
if(index >= 0) index--;
return keys[current];
}
@@ -540,9 +561,8 @@ public class IMMUTABLE_HASH_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERI
@Override
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
current = next;
current = previous = next;
next = (int)(links[current]);
previous = current;
if(index >= 0) index++;
return keys[current];
}
src/builder/resources/speiger/assets/collections/templates/sets/LinkedOpenCustomHashSet.template
+24 -4
View File
@@ -717,6 +717,28 @@ public class LINKED_CUSTOM_HASH_SET KEY_GENERIC_TYPE extends CUSTOM_HASH_SET KEY
return previous != -1;
}
@Override
public int skip(int amount) {
int result = 0;
while(next != -1 && result != amount) {
current = previous = next;
next = (int)(links[current]);
result++;
}
return result;
}
@Override
public int back(int amount) {
int result = 0;
while(previous != -1 && result != amount) {
current = next = previous;
previous = (int)(links[current] >> 32);
result++;
}
return result;
}
@Override
public int nextIndex() {
ensureIndexKnown();
@@ -775,9 +797,8 @@ public class LINKED_CUSTOM_HASH_SET KEY_GENERIC_TYPE extends CUSTOM_HASH_SET KEY
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
current = previous;
current = next = previous;
previous = (int)(links[current] >> 32);
next = current;
if(index >= 0) index--;
return keys[current];
}
@@ -785,9 +806,8 @@ public class LINKED_CUSTOM_HASH_SET KEY_GENERIC_TYPE extends CUSTOM_HASH_SET KEY
@Override
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
current = next;
current = previous = next;
next = (int)(links[current]);
previous = current;
if(index >= 0) index++;
return keys[current];
}
src/builder/resources/speiger/assets/collections/templates/sets/LinkedOpenHashSet.template
+24 -4
View File
@@ -678,6 +678,28 @@ public class LINKED_HASH_SET KEY_GENERIC_TYPE extends HASH_SET KEY_GENERIC_TYPE
}
}
@Override
public int skip(int amount) {
int result = 0;
while(next != -1 && result != amount) {
current = previous = next;
next = (int)(links[current]);
result++;
}
return result;
}
@Override
public int back(int amount) {
int result = 0;
while(previous != -1 && result != amount) {
current = next = previous;
previous = (int)(links[current] >> 32);
result++;
}
return result;
}
@Override
public boolean hasNext() {
return next != -1;
@@ -746,9 +768,8 @@ public class LINKED_HASH_SET KEY_GENERIC_TYPE extends HASH_SET KEY_GENERIC_TYPE
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
current = previous;
current = next = previous;
previous = (int)(links[current] >> 32);
next = current;
if(index >= 0) index--;
return keys[current];
}
@@ -756,9 +777,8 @@ public class LINKED_HASH_SET KEY_GENERIC_TYPE extends HASH_SET KEY_GENERIC_TYPE
@Override
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
current = next;
current = previous = next;
next = (int)(links[current]);
previous = current;
if(index >= 0) index++;
return keys[current];
}
src/builder/resources/speiger/assets/collections/templates/sets/RBTreeSet.template
+40 -16
View File
@@ -1359,6 +1359,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
boolean unboundForwardFence;
boolean unboundBackwardFence;
@@ -1368,6 +1369,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public AscendingSubSetIterator(Entry KEY_GENERIC_TYPE first, Entry KEY_GENERIC_TYPE forwardFence, Entry KEY_GENERIC_TYPE backwardFence)
{
next = first;
previous = first == null ? null : first.previous();
this.forwardFence = forwardFence == null ? EMPTY_KEY_VALUE : forwardFence.key;
this.backwardFence = backwardFence == null ? EMPTY_KEY_VALUE : backwardFence.key;
unboundForwardFence = forwardFence == null;
@@ -1383,6 +1385,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.next();
forwards = true;
@@ -1391,15 +1394,16 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null && (unboundBackwardFence || next.key != backwardFence);
return previous != null && (unboundBackwardFence || previous.key != backwardFence);
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.previous();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.previous();
forwards = false;
return result;
}
@@ -1407,6 +1411,8 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(previous == lastReturned) previous = previous.previous();
if(next == lastReturned) next = next.next();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
set.removeNode(lastReturned);
lastReturned = null;
@@ -1417,6 +1423,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
boolean unboundForwardFence;
boolean unboundBackwardFence;
@@ -1426,6 +1433,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public DescendingSubSetIterator(Entry KEY_GENERIC_TYPE first, Entry KEY_GENERIC_TYPE forwardFence, Entry KEY_GENERIC_TYPE backwardFence)
{
next = first;
previous = first == null ? null : first.next();
this.forwardFence = forwardFence == null ? EMPTY_KEY_VALUE : forwardFence.key;
this.backwardFence = backwardFence == null ? EMPTY_KEY_VALUE : backwardFence.key;
unboundForwardFence = forwardFence == null;
@@ -1441,6 +1449,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.previous();
forwards = false;
@@ -1449,15 +1458,16 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null && (unboundBackwardFence || next.key != backwardFence);
return previous != null && (unboundBackwardFence || previous.key != backwardFence);
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.next();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.next();
forwards = true;
return result;
}
@@ -1465,6 +1475,8 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(previous == lastReturned) previous = previous.next();
if(next == lastReturned) next = next.previous();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
set.removeNode(lastReturned);
lastReturned = null;
@@ -1476,11 +1488,13 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
public AscendingSetIterator(Entry KEY_GENERIC_TYPE first)
{
next = first;
previous = first == null ? null : first.previous();
}
@Override
@@ -1492,6 +1506,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.next();
forwards = true;
@@ -1500,15 +1515,16 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null;
return previous != null;
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.previous();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.previous();
forwards = false;
return result;
}
@@ -1516,6 +1532,8 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(lastReturned == previous) previous = previous.previous();
if(lastReturned == next) next = next.next();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
removeNode(lastReturned);
lastReturned = null;
@@ -1526,11 +1544,13 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
{
Entry KEY_GENERIC_TYPE lastReturned;
Entry KEY_GENERIC_TYPE next;
Entry KEY_GENERIC_TYPE previous;
boolean forwards = false;
public DescendingSetIterator(Entry KEY_GENERIC_TYPE first)
{
next = first;
previous = first == null ? null : first.next();
}
@Override
@@ -1542,6 +1562,7 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
public KEY_TYPE NEXT() {
if(!hasNext()) throw new NoSuchElementException();
lastReturned = next;
previous = next;
KEY_TYPE result = next.key;
next = next.previous();
forwards = false;
@@ -1550,15 +1571,16 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public boolean hasPrevious() {
return next != null;
return previous != null;
}
@Override
public KEY_TYPE PREVIOUS() {
if(!hasPrevious()) throw new NoSuchElementException();
lastReturned = next;
KEY_TYPE result = next.key;
next = next.next();
lastReturned = previous;
next = previous;
KEY_TYPE result = previous.key;
previous = previous.next();
forwards = true;
return result;
}
@@ -1566,6 +1588,8 @@ public class RB_TREE_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE
@Override
public void remove() {
if(lastReturned == null) throw new IllegalStateException();
if(lastReturned == previous) previous = previous.next();
if(lastReturned == next) next = next.previous();
if(forwards && lastReturned.needsSuccessor()) next = lastReturned;
removeNode(lastReturned);
lastReturned = null;