diff --git a/src/main/java/com/github/tommyettinger/ds/LongFloatMap.java b/src/main/java/com/github/tommyettinger/ds/LongFloatMap.java
index 810a299c..a7d65911 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongFloatMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongFloatMap.java
@@ -25,6 +25,7 @@
 import com.github.tommyettinger.function.LongToFloatFunction;
 import com.github.tommyettinger.ds.support.util.FloatIterator;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.AbstractSet;
 import java.util.Arrays;
@@ -824,7 +825,7 @@ public void truncate (int newSize) {
 	 * @return an {@link Iterator} over {@link Entry} key-value pairs; remove is supported.
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
@@ -1138,7 +1139,7 @@ public EntryIterator (LongFloatMap map) {
 		}
 
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return this;
 		}
 
@@ -1182,7 +1183,7 @@ public Entries (LongFloatMap map) {
 		 * @return an iterator over the elements contained in this collection
 		 */
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return iter;
 		}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongFloatOrderedMap.java b/src/main/java/com/github/tommyettinger/ds/LongFloatOrderedMap.java
index 72305664..3cc2be5f 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongFloatOrderedMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongFloatOrderedMap.java
@@ -23,6 +23,7 @@
 import com.github.tommyettinger.ds.support.sort.LongComparators;
 
 import com.github.tommyettinger.ds.support.util.LongIterator;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Iterator;
 import java.util.Map;
@@ -606,7 +607,7 @@ public Entries entrySet () {
 	 * @return an {@link Iterator} over key-value pairs as {@link Map.Entry} values
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongIntMap.java b/src/main/java/com/github/tommyettinger/ds/LongIntMap.java
index 782e996b..2fdda281 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongIntMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongIntMap.java
@@ -23,6 +23,7 @@
 import com.github.tommyettinger.function.LongIntBiConsumer;
 import com.github.tommyettinger.function.LongIntToIntBiFunction;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.AbstractSet;
 import java.util.Arrays;
@@ -781,7 +782,7 @@ public void truncate (int newSize) {
 	 * @return an {@link Iterator} over {@link Entry} key-value pairs; remove is supported.
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
@@ -1095,7 +1096,7 @@ public EntryIterator (LongIntMap map) {
 		}
 
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return this;
 		}
 
@@ -1139,7 +1140,7 @@ public Entries (LongIntMap map) {
 		 * @return an iterator over the elements contained in this collection
 		 */
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return iter;
 		}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongIntOrderedMap.java b/src/main/java/com/github/tommyettinger/ds/LongIntOrderedMap.java
index ee632cde..da274664 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongIntOrderedMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongIntOrderedMap.java
@@ -23,6 +23,7 @@
 import com.github.tommyettinger.ds.support.sort.LongComparators;
 
 import com.github.tommyettinger.ds.support.util.LongIterator;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Iterator;
 import java.util.Map;
@@ -607,7 +608,7 @@ public Entries entrySet () {
 	 * @return an {@link Iterator} over key-value pairs as {@link Map.Entry} values
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongLongMap.java b/src/main/java/com/github/tommyettinger/ds/LongLongMap.java
index 76eedf8d..8d96a972 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongLongMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongLongMap.java
@@ -21,6 +21,7 @@
 import com.github.tommyettinger.ds.support.util.LongIterator;
 import com.github.tommyettinger.function.LongLongBiConsumer;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.AbstractSet;
 import java.util.Arrays;
@@ -781,7 +782,7 @@ public void truncate (int newSize) {
 	 * @return an {@link Iterator} over {@link Entry} key-value pairs; remove is supported.
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull  EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
@@ -1094,7 +1095,7 @@ public EntryIterator (LongLongMap map) {
 		}
 
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return this;
 		}
 
@@ -1138,7 +1139,7 @@ public Entries (LongLongMap map) {
 		 * @return an iterator over the elements contained in this collection
 		 */
 		@Override
-		public Iterator<Entry> iterator () {
+		public @NonNull EntryIterator iterator () {
 			return iter;
 		}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongLongOrderedMap.java b/src/main/java/com/github/tommyettinger/ds/LongLongOrderedMap.java
index 63764933..93fe264d 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongLongOrderedMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongLongOrderedMap.java
@@ -21,6 +21,7 @@
 import com.github.tommyettinger.ds.support.sort.LongComparators;
 
 import com.github.tommyettinger.ds.support.util.LongIterator;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Iterator;
 import java.util.Map;
@@ -604,7 +605,7 @@ public Entries entrySet () {
 	 * @return an {@link Iterator} over key-value pairs as {@link Map.Entry} values
 	 */
 	@Override
-	public Iterator<Entry> iterator () {
+	public @NonNull EntryIterator iterator () {
 		return entrySet().iterator();
 	}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongObjectMap.java b/src/main/java/com/github/tommyettinger/ds/LongObjectMap.java
index 284cb0e5..38405679 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongObjectMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongObjectMap.java
@@ -23,6 +23,7 @@
 import com.github.tommyettinger.function.LongObjToObjBiFunction;
 
 import com.github.tommyettinger.function.LongToObjFunction;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.AbstractCollection;
 import java.util.AbstractSet;
@@ -782,7 +783,7 @@ public void truncate (int newSize) {
 	 * @return an {@link Iterator} over {@link Entry} key-value pairs; remove is supported.
 	 */
 	@Override
-	public Iterator<Entry<V>> iterator () {
+	public @NonNull EntryIterator<V> iterator () {
 		return entrySet().iterator();
 	}
 
@@ -1100,7 +1101,7 @@ public EntryIterator (LongObjectMap<V> map) {
 		}
 
 		@Override
-		public Iterator<Entry<V>> iterator () {
+		public @NonNull EntryIterator<V> iterator () {
 			return this;
 		}
 
@@ -1144,7 +1145,7 @@ public Entries (LongObjectMap<V> map) {
 		 * @return an iterator over the elements contained in this collection
 		 */
 		@Override
-		public Iterator<Entry<V>> iterator () {
+		public @NonNull EntryIterator<V> iterator () {
 			return iter;
 		}
 
@@ -1253,7 +1254,7 @@ public void clear () {
 		 * @return an iterator over the elements contained in this collection
 		 */
 		@Override
-		public Iterator<V> iterator () {
+		public @NonNull ValueIterator<V> iterator () {
 			return iter;
 		}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/LongObjectOrderedMap.java b/src/main/java/com/github/tommyettinger/ds/LongObjectOrderedMap.java
index 097b7ce4..094469fb 100644
--- a/src/main/java/com/github/tommyettinger/ds/LongObjectOrderedMap.java
+++ b/src/main/java/com/github/tommyettinger/ds/LongObjectOrderedMap.java
@@ -21,6 +21,7 @@
 import com.github.tommyettinger.ds.support.sort.LongComparators;
 
 import com.github.tommyettinger.ds.support.util.LongIterator;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Collection;
 import java.util.Comparator;
@@ -587,7 +588,7 @@ public Entries<V> entrySet () {
 	 * @return an {@link Iterator} over key-value pairs as {@link Map.Entry} values
 	 */
 	@Override
-	public Iterator<Entry<V>> iterator () {
+	public @NonNull EntryIterator<V> iterator () {
 		return entrySet().iterator();
 	}
 
diff --git a/src/main/java/com/github/tommyettinger/ds/NumberedSet.java b/src/main/java/com/github/tommyettinger/ds/NumberedSet.java
index b7dce095..6fd63615 100644
--- a/src/main/java/com/github/tommyettinger/ds/NumberedSet.java
+++ b/src/main/java/com/github/tommyettinger/ds/NumberedSet.java
@@ -17,6 +17,7 @@
 
 package com.github.tommyettinger.ds;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Collection;
 import java.util.Iterator;
@@ -343,7 +344,7 @@ public boolean addAll (int insertionIndex, T[] array, int offset, int count) {
 	}
 
 	@Override
-	public boolean retainAll (Collection<?> c) {
+	public boolean retainAll (@NonNull Collection<?> c) {
 		boolean modified = false;
 		Iterator<T> it = iterator();
 		while (it.hasNext()) {
@@ -360,7 +361,7 @@ public boolean retainAll (Collection<?> c) {
 	}
 
 	@Override
-	public boolean removeAll (Collection<?> c) {
+	public boolean removeAll (@NonNull Collection<?> c) {
 		boolean modified = false;
 		Iterator<?> it = iterator();
 		while (it.hasNext()) {
@@ -518,7 +519,7 @@ public void truncate (int newSize) {
 	 * @return a ListIterator, or more specifically a {@link NumberedSetIterator} over this set
 	 */
 	@Override
-	public NumberedSetIterator<T> iterator () {
+	public @NonNull NumberedSetIterator<T> iterator () {
 		if (iterator1 == null || iterator2 == null) {
 			iterator1 = new NumberedSetIterator<>(this);
 			iterator2 = new NumberedSetIterator<>(this);
@@ -601,12 +602,12 @@ public void removeRange (int start, int end) {
 	}
 
 	@Override
-	public Object[] toArray () {
+	public Object @NonNull [] toArray () {
 		return map.keySet().toArray();
 	}
 
 	@Override
-	public <T1> T1[] toArray (T1[] a) {
+	public <T1> T1 @NonNull [] toArray (T1 @NonNull [] a) {
 		return map.keySet().toArray(a);
 	}
 
@@ -902,7 +903,7 @@ public void reset (int index) {
 		 * @return a ListIterator; really this same NumberedSetIterator.
 		 */
 		@Override
-		public NumberedSetIterator<T> iterator () {
+		public @NonNull NumberedSetIterator<T> iterator () {
 			return this;
 		}
 	}
diff --git a/src/main/java/com/github/tommyettinger/ds/ObjectDeque.java b/src/main/java/com/github/tommyettinger/ds/ObjectDeque.java
index 6a29b0ec..c9175777 100644
--- a/src/main/java/com/github/tommyettinger/ds/ObjectDeque.java
+++ b/src/main/java/com/github/tommyettinger/ds/ObjectDeque.java
@@ -17,6 +17,7 @@
 
 package com.github.tommyettinger.ds;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.Arrays;
 import java.util.Collection;
@@ -815,7 +816,7 @@ public int size () {
 	 * type} is {@code Object}, containing all of the elements in this collection
 	 */
 	@Override
-	public Object[] toArray () {
+	public Object @NonNull [] toArray () {
 		Object[] next = new Object[size];
 		if (head < tail) {
 			System.arraycopy(values, head, next, 0, tail - head);
@@ -854,7 +855,7 @@ public Object[] toArray () {
 	 * @throws NullPointerException if the specified array is null
 	 */
 	@Override
-	public <E> E[] toArray (E[] a) {
+	public <E> E @NonNull [] toArray (E[] a) {
 		int oldSize = size;
 		if (a.length < oldSize) {
 			a = Arrays.copyOf(a, oldSize);
@@ -1260,7 +1261,7 @@ public void clear () {
 	 * iteration, use {@link ObjectDequeIterator#ObjectDequeIterator(ObjectDeque)}.
 	 */
 	@Override
-	public ObjectDequeIterator<T> iterator () {
+	public @NonNull ObjectDequeIterator<T> iterator () {
 		if (iterator1 == null || iterator2 == null) {
 			iterator1 = new ObjectDequeIterator<>(this);
 			iterator2 = new ObjectDequeIterator<>(this);
@@ -1288,7 +1289,7 @@ public ObjectDequeIterator<T> iterator () {
 	 * @return an iterator over the elements in this deque in reverse sequence
 	 */
 	@Override
-	public ObjectDequeIterator<T> descendingIterator () {
+	public @NonNull ObjectDequeIterator<T> descendingIterator () {
 		if (descendingIterator1 == null || descendingIterator2 == null) {
 			descendingIterator1 = new ObjectDequeIterator<>(this, true);
 			descendingIterator2 = new ObjectDequeIterator<>(this, true);
@@ -1750,7 +1751,7 @@ public void reset (int index) {
 		 * @return a ListIterator; really this same ObjectDequeIterator.
 		 */
 		@Override
-		public ObjectDequeIterator<T> iterator () {
+		public @NonNull ObjectDequeIterator<T> iterator () {
 			return this;
 		}
 	}
diff --git a/src/main/java/com/github/tommyettinger/ds/ObjectList.java b/src/main/java/com/github/tommyettinger/ds/ObjectList.java
index 534276c9..cf7b2ba2 100644
--- a/src/main/java/com/github/tommyettinger/ds/ObjectList.java
+++ b/src/main/java/com/github/tommyettinger/ds/ObjectList.java
@@ -19,6 +19,7 @@
 
 import com.github.tommyettinger.ds.support.sort.ObjectComparators;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -491,7 +492,7 @@ public StringBuilder builderAppend (StringBuilder builder, String separator) {
 	 * @throws IndexOutOfBoundsException {@inheritDoc}
 	 */
 	@Override
-	public ObjectListIterator<T> listIterator (int index) {
+	public @NonNull ObjectListIterator<T> listIterator (int index) {
 		if (iterator1 == null || iterator2 == null) {
 			iterator1 = new ObjectListIterator<>(this, index);
 			iterator2 = new ObjectListIterator<>(this, index);
@@ -517,7 +518,7 @@ public ObjectListIterator<T> listIterator (int index) {
 	 * @see #listIterator(int)
 	 */
 	@Override
-	public ObjectListIterator<T> listIterator () {
+	public @NonNull ObjectListIterator<T> listIterator () {
 		if (iterator1 == null || iterator2 == null) {
 			iterator1 = new ObjectListIterator<>(this);
 			iterator2 = new ObjectListIterator<>(this);
@@ -543,7 +544,7 @@ public ObjectListIterator<T> listIterator () {
 	 * @return an iterator over the elements in this list in proper sequence
 	 */
 	@Override
-	public ObjectListIterator<T> iterator () {
+	public @NonNull ObjectListIterator<T> iterator () {
 		if (iterator1 == null || iterator2 == null) {
 			iterator1 = new ObjectListIterator<>(this);
 			iterator2 = new ObjectListIterator<>(this);
@@ -767,7 +768,7 @@ public void reset (int index) {
 		 * @return a ListIterator; really this same ObjectListIterator.
 		 */
 		@Override
-		public ObjectListIterator<T> iterator () {
+		public @NonNull ObjectListIterator<T> iterator () {
 			return this;
 		}
 	}