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0.6 Update
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This changes does not change functionality and will not break any
implementation. All changes are internal only.

Changes to Collection Class:
1) Updated contains to just use collection.stream.anyMatch
2) Added parameter guards to protect against invalid elements
3) get() will throw an illegal state exception if the collection is
empty
4) get() asserts object is not null (Which if the collection contains
elements, it never should be).
5) JavaDoc has been updated to document these changes

Changes to Tests:
1) Added new tests to assert all errors are thrown correctly
2) Added new test to assert get() never returns null in extreme edge
cases
3) Increased repeated test amounts
4) Updated int comparison to use assertEquals not assertTrue x == y
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@lewysDavies
lewysDavies committed Jul 8, 2020
1 parent 75d2f12 commit b188011
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Showing 2 changed files with 155 additions and 45 deletions.
63 changes: 47 additions & 16 deletions src/main/java/com/lewdev/probabilitylib/ProbabilityCollection.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

import java.util.Comparator;
import java.util.Iterator;
import java.util.Objects;
import java.util.TreeSet;
import java.util.concurrent.ThreadLocalRandom;

Expand All @@ -22,7 +23,7 @@
* </ul>
*
* @author Lewys Davies
* @version 0.5
* @version 0.6
*
* @param <E> Type of elements
*/
Expand Down Expand Up @@ -60,12 +61,15 @@ public boolean isEmpty() {
/**
* @param object
* @return True if the collection contains the object, else False
* @throws IllegalArgumentException if object null
*/
public boolean contains(E object) {
if(object == null) {
throw new IllegalArgumentException("Cannot check if null object is contained in a collection");
}

return this.collection.stream()
.filter(entry -> entry.getObject().equals(object))
.findFirst()
.isPresent();
.anyMatch(entry -> entry.getObject().equals(object));
}

/**
Expand All @@ -78,12 +82,24 @@ public Iterator<ProbabilitySetElement<E>> iterator() {
/**
* Add an object to this collection
*
* @param object
* @param probability share
* @param object. Not null.
* @param probability share. Must be greater than 0.
*
* @throws IllegalArgumentException if object is null
* @throws IllegalArgumentException if probability <= 0
*/
public void add(E object, int probability) {
if(object == null) {
throw new IllegalArgumentException("Cannot add null object");
}

if(probability <= 0) {
throw new IllegalArgumentException("Probability must be greater than 0");
}

this.collection.add(new ProbabilitySetElement<E>(object, probability));
this.totalProbability += probability;

this.updateIndexes();
}

Expand All @@ -92,32 +108,46 @@ public void add(E object, int probability) {
*
* @param object
* @return True if object was removed, else False.
*
* @throws IllegalArgumentException if object null
*/
public boolean remove(E object) {
if(object == null) {
throw new IllegalArgumentException("Cannot remove null object");
}

Iterator<ProbabilitySetElement<E>> it = this.iterator();
boolean removed = false;
boolean removed = it.hasNext();

while(it.hasNext()) {
ProbabilitySetElement<E> element = it.next();
if(element.getObject().equals(object)) {
removed = true;
this.totalProbability -= element.getProbability();
ProbabilitySetElement<E> entry = it.next();
if(entry.getObject().equals(object)) {
this.totalProbability -= entry.getProbability();
it.remove();
}
}

this.updateIndexes();

return removed;
}

/**
* @return Random object based on probability
* Get a random object from this collection, based on probability.
*
* @return <E> Random object
*
* @throws IllegalStateException if this collection is empty
*/
public E get() {
if(this.isEmpty()) {
throw new IllegalStateException("Cannot get an element out of a empty set");
}

ProbabilitySetElement<E> toFind = new ProbabilitySetElement<>(null, 0);
toFind.setIndex(ThreadLocalRandom.current().nextInt(1, this.totalProbability + 1));

return this.collection.floor(toFind).getObject();
return Objects.requireNonNull(this.collection.floor(toFind).getObject());
}

/**
Expand All @@ -131,7 +161,8 @@ public final int getTotalProbability() {
* Calculate the size of all element's "block" of space:
* i.e 1-5, 6-10, 11-14, 15, 16
*
* We then only need to store the start index of each element
* We then only need to store the start index of each element,
* as we make use of the TreeSet#floor
*/
private void updateIndexes() {
int previousIndex = 0;
Expand Down Expand Up @@ -182,12 +213,12 @@ public final int getProbability() {
}

// Used internally, see this class's documentation
protected final int getIndex() {
private final int getIndex() {
return this.index;
}

// Used Internally, see this class's documentation
protected final int setIndex(int index) {
private final int setIndex(int index) {
this.index = index;
return this.index;
}
Expand Down
137 changes: 108 additions & 29 deletions src/test/java/com/lewdev/probabilitylib/ProbabilityCollectionTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,14 @@
import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.Test;

/**
* @author Lewys Davies
*/
public class ProbabilityCollectionTest {

@RepeatedTest(value = 1000)
@RepeatedTest(value = 10_000)
public void test_insert() {
ProbabilityCollection<String> collection = new ProbabilityCollection<>();
assertEquals(0, collection.size());
Expand Down Expand Up @@ -44,12 +45,12 @@ public void test_insert() {
}
}

@RepeatedTest(value = 1000)
@RepeatedTest(value = 10_000)
public void test_remove() {
ProbabilityCollection<String> collection = new ProbabilityCollection<>();
assertTrue(collection.size() == 0);
assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 0);
assertEquals(0, collection.getTotalProbability());

String t1 = "Hello";
String t2 = "World";
Expand All @@ -59,33 +60,36 @@ public void test_remove() {
collection.add(t2, 10);
collection.add(t3, 10);

assertTrue(collection.size() == 3);
assertEquals(3, collection.size());
assertFalse(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 30);
assertEquals(30, collection.getTotalProbability());

collection.remove(t2);
// Remove t2
assertTrue(collection.remove(t2));

assertTrue(collection.size() == 2);
assertEquals(2, collection.size());
assertFalse(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 20);
assertEquals(20, collection.getTotalProbability());

collection.remove(t1);
// Remove t1
assertTrue(collection.remove(t1));

assertTrue(collection.size() == 1);
assertEquals(1, collection.size());
assertFalse(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 10);
assertEquals(10, collection.getTotalProbability());

collection.remove(t3);
//Remove t3
assertTrue(collection.remove(t3));

assertTrue(collection.size() == 0);
assertTrue(collection.getTotalProbability() == 0);
assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());
}

@RepeatedTest(value = 1000)
@RepeatedTest(value = 10_000)
public void test_remove_duplicates() {
ProbabilityCollection<String> collection = new ProbabilityCollection<>();
assertTrue(collection.size() == 0);
assertEquals(0, collection.size());
assertTrue(collection.isEmpty());

String t1 = "Hello";
Expand All @@ -104,27 +108,30 @@ public void test_remove_duplicates() {
collection.add(t3, 10);
}

assertTrue(collection.size() == 30);
assertEquals(30, collection.size());
assertFalse(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 300);
assertEquals(300, collection.getTotalProbability());

collection.remove(t2);
//Remove t2
assertTrue(collection.remove(t2));

assertTrue(collection.size() == 20);
assertEquals(20, collection.size());
assertFalse(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 200);
assertEquals(200, collection.getTotalProbability());

collection.remove(t1);
// Remove t1
assertTrue(collection.remove(t1));

assertTrue(collection.size() == 10);
assertEquals(10, collection.size());
assertFalse(collection.isEmpty());
assertEquals(100, collection.getTotalProbability());

assertTrue(collection.getTotalProbability() == 100);
collection.remove(t3);
//Remove t3
assertTrue(collection.remove(t3));

assertTrue(collection.size() == 0);
assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertTrue(collection.getTotalProbability() == 0);
assertEquals(0, collection.getTotalProbability());
}

@RepeatedTest(1_000_000)
Expand Down Expand Up @@ -159,10 +166,82 @@ public void test_probability() {
double bResult = b / (double) totalGets * 100;
double cResult = c / (double) totalGets * 100;

double acceptableDeviation = 1;
double acceptableDeviation = 1; // %

assertTrue(Math.abs(aProb - aResult) <= acceptableDeviation);
assertTrue(Math.abs(bProb - bResult) <= acceptableDeviation);
assertTrue(Math.abs(cProb - cResult) <= acceptableDeviation);
}

@RepeatedTest(1_000_000)
public void test_get_never_null() {
ProbabilityCollection<String> collection = new ProbabilityCollection<>();
// Tests get will never return null
// Just one smallest element get, must not return null
collection.add("A", 1);
assertNotNull(collection.get());

// Reset state
collection.remove("A");
assertEquals(0, collection.size());
assertTrue(collection.isEmpty());

// Just one large element, must not return null
collection.add("A", 5_000_000);
assertNotNull(collection.get());
}

@Test
public void test_Errors() {
ProbabilityCollection<String> collection = new ProbabilityCollection<>();

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());

// Cannot get from empty collection
assertThrows(IllegalStateException.class, () -> {
collection.get();
});

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());

// Cannot add null object
assertThrows(IllegalArgumentException.class, () -> {
collection.add(null, 1);
});

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());

// Cannot add prob 0
assertThrows(IllegalArgumentException.class, () -> {
collection.add("A", 0);
});

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());

// Cannot remove null
assertThrows(IllegalArgumentException.class, () -> {
collection.remove(null);
});

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());

// Cannot contains null
assertThrows(IllegalArgumentException.class, () -> {
collection.contains(null);
});

assertEquals(0, collection.size());
assertTrue(collection.isEmpty());
assertEquals(0, collection.getTotalProbability());
}
}

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