Minor changes

1) Use SplittableRandom instead of ThreadLocalRandom, for slightly
improved performance and higher quality simulation
2) JavaDoc comments update
3) Finalised more methods that shall never be overridden, based on this
probability implementation

Author: lewysDavies

src/main/java/com/lewdev/probabilitylib/ProbabilityCollection.java

@@ -1,10 +1,31 @@
+/*
+* Copyright (c) 2020 Lewys Davies
+* 
+* Permission is hereby granted, free of charge, to any person obtaining a copy
+* of this software and associated documentation files (the "Software"), to deal
+* in the Software without restriction, including without limitation the rights
+* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+* copies of the Software, and to permit persons to whom the Software is
+* furnished to do so, subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in all
+* copies or substantial portions of the Software.
+* 
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+* SOFTWARE.
+*/
 package com.lewdev.probabilitylib;
 
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.Objects;
+import java.util.SplittableRandom;
 import java.util.TreeSet;
-import java.util.concurrent.ThreadLocalRandom;
 
 /**
  * ProbabilityCollection for retrieving random elements based on probability.
@@ -28,19 +49,17 @@
  * @param <E> Type of elements
  */
 public class ProbabilityCollection<E> {
-
-	protected final Comparator<ProbabilitySetElement<E>> comparator = 
-			(o1, o2)-> Integer.compare(o1.getIndex(), o2.getIndex());
 
 	private final TreeSet<ProbabilitySetElement<E>> collection;
+	private final SplittableRandom random = new SplittableRandom();
 
 	private int totalProbability;
 
 	/**
 	 * Construct a new Probability Collection
 	 */
 	public ProbabilityCollection() {
-		this.collection = new TreeSet<>(this.comparator);
+		this.collection = new TreeSet<>(Comparator.comparingInt(ProbabilitySetElement::getIndex));
 		this.totalProbability = 0;
 	}
 
@@ -52,28 +71,28 @@ public int size() {
 	}
 
 	/**
-	 * @return Collection contains no elements
+	 * @return True if collection contains no elements, else False
 	 */
 	public boolean isEmpty() {
 		return this.collection.isEmpty();
 	}
 
 	/**
-	 * @param object
-	 * @return True if the collection contains the object, else False
-	 * @throws IllegalArgumentException if object null
+	 * @param <E> object
+	 * @return True if collection contains the object, else False
+	 * @throws IllegalArgumentException if object is null
 	 */
 	public boolean contains(E object) {
 		if(object == null) {
-			throw new IllegalArgumentException("Cannot check if null object is contained in a collection");
+			throw new IllegalArgumentException("Cannot check if null object is contained in this collection");
 		}
 
 		return this.collection.stream()
 			.anyMatch(entry -> entry.getObject().equals(object));
 	}
 
 	/**
-	 * @return Iterator over collection
+	 * @return Iterator over this collection
 	 */
 	public Iterator<ProbabilitySetElement<E>> iterator() {
 		return this.collection.iterator();
@@ -82,7 +101,7 @@ public Iterator<ProbabilitySetElement<E>> iterator() {
 	/**
 	 * Add an object to this collection
 	 * 
-	 * @param object. Not null.
+	 * @param <E> object. Not null.
 	 * @param probability share. Must be greater than 0.
 	 * 
 	 * @throws IllegalArgumentException if object is null
@@ -106,10 +125,10 @@ public void add(E object, int probability) {
 	/**
 	 * Remove a object from this collection
 	 * 
-	 * @param object
+	 * @param <E> object
 	 * @return True if object was removed, else False.
 	 * 
-	 * @throws IllegalArgumentException if object null
+	 * @throws IllegalArgumentException if object is null
 	 */
 	public boolean remove(E object) {
 		if(object == null) {
@@ -141,11 +160,11 @@ public boolean remove(E object) {
 	 */
 	public E get() {
 		if(this.isEmpty()) {
-			throw new IllegalStateException("Cannot get an element out of a empty set");
+			throw new IllegalStateException("Cannot get an element out of a empty collection");
 		}
 
 		ProbabilitySetElement<E> toFind = new ProbabilitySetElement<>(null, 0);
-		toFind.setIndex(ThreadLocalRandom.current().nextInt(1, this.totalProbability + 1));
+		toFind.setIndex(this.random.nextInt(1, this.totalProbability + 1));
 
 		return Objects.requireNonNull(this.collection.floor(toFind).getObject());
 	}
@@ -164,7 +183,7 @@ public final int getTotalProbability() {
 	 * We then only need to store the start index of each element,
 	 * as we make use of the TreeSet#floor
 	 */
-	private void updateIndexes() {
+	private final void updateIndexes() {
 		int previousIndex = 0;
 
 		for(ProbabilitySetElement<E> entry : this.collection) {
@@ -190,7 +209,7 @@ final static class ProbabilitySetElement<T> {
 		private int index;
 
 		/**
-		 * @param object
+		 * @param <T> object
 		 * @param probability
 		 */
 		protected ProbabilitySetElement(T object, int probability) {
@@ -199,7 +218,7 @@ protected ProbabilitySetElement(T object, int probability) {
 		}
 
 		/**
-		 * @return The actual object
+		 * @return <T> The actual object
 		 */
 		public final T getObject() {
 			return this.object;