grow the array only by 50%

The old implementation grew the array by 100% with each resize.
The new implementation reduces the memory usage for, especially
for large lists.
The new algorithm is overflow-concious.

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

@@ -13,6 +13,11 @@ public class IntList {
 
 	private static final int DEFAULT_CAPACITY = 10;
 
+	/**
+	 * The maximum size of an array.
+	 */
+	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
 	private int[] data;
 
 	private int index = 0;
@@ -33,16 +38,16 @@ public class IntList {
 	 *             if initial capacity is negative
 	 */
 	public IntList(final int initialCapacity) {
-		if (initialCapacity < 0) {
-			throw new IllegalArgumentException("initial capacity must not be negative");
+		if (initialCapacity < 0 || initialCapacity > MAX_ARRAY_SIZE) {
+			throw new IllegalArgumentException(
+					"initial capacity must not be negative and not larger than " + MAX_ARRAY_SIZE);
 		}
 
 		data = new int[initialCapacity];
 	}
 
 	/**
-	 * Create a new {@link IntList} with a copy of the elements of
-	 * {@code intList}.
+	 * Create a new {@link IntList} with a copy of the elements of {@code intList}.
 	 *
 	 * @param intList
 	 *            the list to copy
@@ -172,9 +177,8 @@ public class IntList {
 	 * @param length
 	 *            number of elements to remove
 	 * @throws IndexOutOfBoundsException
-	 *             if {@code from} or {@code length} is negative, or if the
-	 *             range defined by {@code from} and {@code length} is out of
-	 *             bounds
+	 *             if {@code from} or {@code length} is negative, or if the range
+	 *             defined by {@code from} and {@code length} is out of bounds
 	 */
 	public void remove(final int from, final int length) {
 
@@ -221,9 +225,8 @@ public class IntList {
 	 *            number of elements
 	 * @return the {@code length} elements starting at {@code from}
 	 * @throws IndexOutOfBoundsException
-	 *             if {@code from} or {@code length} is negative, or if the
-	 *             range defined by {@code from} and {@code length} is out of
-	 *             bounds
+	 *             if {@code from} or {@code length} is negative, or if the range
+	 *             defined by {@code from} and {@code length} is out of bounds
 	 */
 	public int[] get(final int from, final int length) {
 		if (from < 0) {
@@ -260,12 +263,17 @@ public class IntList {
 	private void ensureCapacity(final int newElements) {
 
 		final int requiredCapacity = index + newElements;
-		if (requiredCapacity - 1 >= data.length) {
-			final int newCapacity = data.length * 2 > requiredCapacity ? data.length * 2 : requiredCapacity;
+		if (requiredCapacity < 0 || requiredCapacity > MAX_ARRAY_SIZE) {
+			// overflow, or too big
+			throw new OutOfMemoryError();
+		}
+		if (requiredCapacity > data.length) {
 
-			final int[] newData = new int[newCapacity];
-			System.arraycopy(data, 0, newData, 0, index);
-			data = newData;
+			int newCapacity = data.length + data.length / 2;
+			newCapacity = Math.max(requiredCapacity, newCapacity);
+			newCapacity = Math.min(MAX_ARRAY_SIZE, newCapacity);
+
+			data = Arrays.copyOf(data, newCapacity);
 		}
 	}