add maxCapacity to LongLongHashMap

This allows us to define an upper limit for the memory usage.

primitiveCollections/build.gradle

@@ -1,6 +1,6 @@
 
 group='org.lucares'
-version = '0.2'
+version = '0.3'
 
 dependencies {
 	jmh 'org.eclipse.collections:eclipse-collections:10.2.0'

primitiveCollections/src/main/java/org/lucares/collections/LongLongHashMap.java

@@ -46,6 +46,8 @@ public class LongLongHashMap {
 	 */
 	private Long removedKeyValue = null;
 
+	private int maxCapacity = MAX_ARRAY_SIZE;
+
 	/**
 	 * Create a new {@link LongLongHashMap} with the given initial capacity and load
 	 * factor.
@@ -78,6 +80,30 @@ public class LongLongHashMap {
 		this(8, 0.75);
 	}
 
+
+	/**
+	 * Sets the maximum capacity.<p>
+	 * This restricts the maximum memory used by this map. The memory consumption can be twice as much during grow or shrink phases.
+	 * <p>
+	 * Note that the performance can suffer if the map contains more keys than capacity time loadFactor.
+	 * <p>
+	 * Note an automatic {@link #rehash()} is triggered if the new maxCapacity is smaller than the current capacity. 
+	 * But there is not automatic rehash when the new maxCapacity is greater than the current capacity. 
+	 * 
+	 * @param maxCapacity new maximum capacity
+	 * @throws IllegalArgumentException if {@code maxCapacity} is smaller than {@link #size()}
+	 */
+	public void setMaxCapacity(int maxCapacity) {
+		if (maxCapacity < size) {
+			throw new IllegalArgumentException("maxCapacity must equal or larger than current size of the map");
+		}
+		this.maxCapacity = maxCapacity;
+		
+		if (maxCapacity < keys.length) {			
+			rehash(maxCapacity);
+		}
+	}
+
 	/**
 	 * The number of entries in this map.
 	 *
@@ -144,9 +170,14 @@ public class LongLongHashMap {
 	 *
 	 * @param key   the key
 	 * @param value the value
+	 * @throws IllegalStateException if the map is full, see {@link #setMaxCapacity(int)}
 	 */
 	public void put(final long key, final long value) {
 
+		if (size == maxCapacity) {
+			throw new IllegalStateException("map is full");
+		}
+		
 		if (key == NULL_KEY) {
 			size += zeroValue == null ? 1 : 0;
 			zeroValue = value;
@@ -448,8 +479,10 @@ public class LongLongHashMap {
 	}
 
 	private void growAndRehash() {
-		final int newSize = Math.min(keys.length * 2, MAX_ARRAY_SIZE);
+		final int newSize = Math.min(keys.length * 2, maxCapacity);
-		rehash(newSize);
+		if(newSize != keys.length) {
+			rehash(newSize);
+		}
 	}
 
 	private void rehash(int newSize) {

primitiveCollections/src/test/java/org/lucares/collections/LongLongHashMapTest.java

@@ -1,5 +1,7 @@
 package org.lucares.collections;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import java.util.Random;
 import java.util.stream.LongStream;
 
@@ -54,14 +56,25 @@ public class LongLongHashMapTest {
 		final LongLongHashMap map = new LongLongHashMap();
 		final int values = 100;
 
-		fillMap(map, values); // fill with keys 0...99
+		 // fill with keys 0...99
+		for (int i = 0; i < values; i++) {
+			map.put(i, i);
+		}
 
 		map.remove(values); // key does not exist
 		Assertions.assertEquals(values, map.size(), "size after removing non existing key 100");
 
+		// -1 is a sentinel key and has special handling
 		map.remove(-1); // key does not exist
 		Assertions.assertEquals(values, map.size(), "size after removing non existing key -1");
 		
+		map.put(-1, -1);
+		Assertions.assertEquals(values+1, map.size(), "size after adding key -1");
+		
+		map.remove(-1); // key exists
+		Assertions.assertEquals(values, map.size(), "size after removing key -1");
+
+		// 0 is a sentinel key and has special handling
 		map.remove(0); // key exists
 		Assertions.assertEquals(values - 1, map.size(), "size after removing existing key 0");
 
@@ -70,7 +83,9 @@ public class LongLongHashMapTest {
 
 		for (int i = 1; i < 100; i++) {
 			map.remove(i);
+			Assertions.assertEquals(values-i-1, map.size(), "size after removing key "+i);
 		}
+		Assertions.assertEquals(0, map.size(), "size after removing all keys");
 	}
 
 	@Test
@@ -353,6 +368,42 @@ public class LongLongHashMapTest {
 		Assertions.assertEquals(6, LongLongHashMap.findPosOfFirstPositiveKey(new long[] { -1, 0, 0, 0, 0, 0, 1 }));
 	}
 	
+	@Test
+	public void testMaxCapacity() {
+		LongLongHashMap map = new LongLongHashMap(6,0.75);
+		Assertions.assertEquals(6, map.getCapacity());
+		
+		// capacity is reduced to 5 - possible, because map is empty 
+		map.setMaxCapacity(5);
+		Assertions.assertEquals(5, map.getCapacity());
+		
+		map.put(1, 0); 
+		map.put(2, 0);
+		map.put(3, 0);
+		map.put(4, 0);
+		map.put(5, 0);
+		Assertions.assertEquals(5, map.getCapacity());
+		Assertions.assertEquals(5, map.size());
+		
+		// ensure we cannot add more values than the capacity allows
+		// 0 and -1 are sentinels, we have to check them separately
+		assertThrows(IllegalStateException.class, () -> map.put(0, 55));
+		assertThrows(IllegalStateException.class, () -> map.put(-1, 55));
+		assertThrows(IllegalStateException.class, () -> map.put(6, 55));// key is negative to ensure we actually could add it if the capacity restriction was not there
+		
+		Assertions.assertEquals(5, map.size()); // we still have only 5 keys in the map
+		
+		// check that we can increase the maxCapacity
+		map.setMaxCapacity(map.getCapacity()+1);
+		Assertions.assertEquals(5, map.getCapacity()); // capacity was not updated, because there was not need - you would have to manually call rehash()
+		Assertions.assertEquals(5, map.size());
+		map.put(6, 0); 
+		assertThrows(IllegalStateException.class, () -> map.put(7, 55));
+		
+		// check we cannot make the capacity smaller than the current size
+		assertThrows(IllegalArgumentException.class, ()->map.setMaxCapacity(map.size()-1));
+	}
+
 	private LongList findKeysWithSameSpread(final LongLongHashMap map) {
 		final LongList result = new LongList();
 		final int spread = map.spread(1);
@@ -369,10 +420,4 @@ public class LongLongHashMapTest {
 
 		return result;
 	}
-
-	private void fillMap(LongLongHashMap map, int numEntries) {
-		for (int i = 0; i < numEntries; i++) {
-			map.put(i, i);
-		}
-	}
 }