Optimize immutable primitive ArrayList creation from primitive iterab…

…les.

eclipse-collections-code-generator/src/main/resources/api/primitiveIterable.stg

@@ -70,7 +70,26 @@ public interface <name>Iterable extends PrimitiveIterable
  /**
  * Converts the <name>Iterable to a primitive <type> array.
  */
- <type>[] toArray();
+ default <type>[] toArray()
+ {
+ return this.toSizedArray(this.size());
+ }
+
+ /**
+ * Converts the <name>Iterable to a primitive <type> array up to the specified size.
+ *
+ * @since 12.0
+ */
+ default <type>[] toSizedArray(int size)
+ {
+ <type>[] array = new <type>[size];
+ int i = 0;
+ for (<name>Iterator it = this.<type>Iterator(); it.hasNext() && size > i;)
+ {
+ array[i++] = it.next();
+ }
+ return array;
+ }
 
  /**
  * Converts the <name>Iterable to a primitive <type> array. If the collection fits into the provided array it is used

eclipse-collections-code-generator/src/main/resources/impl/bag/mutable/primitiveHashBag.stg

@@ -723,12 +723,18 @@ public class <name>HashBag
  @Override
  public <type>[] toArray()
  {
- <type>[] array = new <type>[this.size()];
+ return this.toSizedArray(this.size());
+ }
+
+ @Override
+ public <type>[] toSizedArray(final int size)
+ {
+ <type>[] array = new <type>[size];
  int[] index = {0};
 
  this.forEachWithOccurrences((<type> each, int occurrences) ->
  {
- for (int i = 0; i \< occurrences; i++)
+ for (int i = 0; index[0] \< size && i \< occurrences; i++)
  {
  array[index[0]] = each;
  index[0]++;

eclipse-collections-code-generator/src/main/resources/impl/lazy/abstractLazyPrimitiveIterable.stg

@@ -235,12 +235,6 @@ public abstract class AbstractLazy<name>Iterable implements Lazy<name>Iterable
  return new Chunk<name>Iterable(this, size);
  }
 
- @Override
- public <type>[] toArray()
- {
- return this.toList().toArray();
- }
-
  @Override
  public Mutable<name>List toList()
  {

eclipse-collections-code-generator/src/main/resources/impl/lazy/tapPrimitiveIterable.stg

@@ -36,6 +36,12 @@ public class Tap<name>Iterable
  this.procedure = procedure;
  }
 
+ @Override
+ public <type>[] toArray()
+ {
+ return this.toSizedArray(this.adapted.size());
+ }
+
  @Override
  public void each(<name>Procedure procedure)
  {

eclipse-collections-code-generator/src/main/resources/impl/list/immutable/immutablePrimitiveArrayList.stg

@@ -86,6 +86,11 @@ final class Immutable<name>ArrayList
  return new Immutable<name>ArrayList(iterable.toArray());
  }
 
+ public static Immutable<name>ArrayList newList(<name>Iterable iterable, int size)
+ {
+ return new Immutable<name>ArrayList(iterable.toSizedArray(size));
+ }
+
  public static Immutable<name>ArrayList newListWith(<type>... elements)
  {
  <type>[] newArray = new <type>[elements.length];

eclipse-collections-code-generator/src/main/resources/impl/list/immutable/immutablePrimitiveListFactoryImpl.stg

@@ -93,15 +93,20 @@ public class Immutable<name>ListFactoryImpl implements Immutable<name>ListFactor
  {
  return (Immutable<name>List) items;
  }
- if (items == null || items.size() == 0)
+ if (items == null)
  {
  return this.with();
  }
- if (items.size() == 1)
+ int size = items.size();
+ if (size == 0)
  {
- return this.with(items.toArray()[0]);
+ return this.with();
+ }
+ if (size == 1)
+ {
+ return this.with(items.<type>Iterator().next());
  }
- return Immutable<name>ArrayList.newList(items);
+ return Immutable<name>ArrayList.newList(items, size);
  }
 
  /**

eclipse-collections-code-generator/src/main/resources/impl/list/mutable/primitiveArrayList.stg

@@ -856,8 +856,15 @@ public class <name>ArrayList extends Abstract<name>Iterable
  @Override
  public <type>[] toArray()
  {
- <type>[] newItems = new <type>[this.size];
- System.arraycopy(this.items, 0, newItems, 0, this.size);
+ return this.toSizedArray(this.size);
+ }
+
+ @Override
+ public <type>[] toSizedArray(int s)
+ {
+ <type>[] newItems = new <type>[s];
+ int newSize = Math.min(s, this.size);
+ System.arraycopy(this.items, 0, newItems, 0, newSize);
  return newItems;
  }
 

eclipse-collections-code-generator/src/main/resources/test/collection/mutable/abstractPrimitiveIterableTestCase.stg

@@ -916,6 +916,28 @@ public void sumConsistentRounding()
  Assert.assertArrayEquals(new <type>[]{<(literal.(type))("32")>}, this.newWith(<(literal.(type))("32")>).toArray()<(delta.(type))>);
  }
 
+ @Test
+ public void toSizedArray()
+ {
+ <name>Iterable iterable = this.newWith(<["1", "2"]:(literal.(type))(); separator=", ">);
+ <type>[] sizeThree = iterable.toSizedArray(3);
+ Assert.assertTrue(Arrays.equals(new <type>[]{<["1", "2", "0"]:(literal.(type))(); separator=", ">}, sizeThree)
+ || Arrays.equals(new <type>[]{<["2", "1", "0"]:(literal.(type))(); separator=", ">}, sizeThree)
+ || Arrays.equals(new <type>[]{<["0", "1", "2"]:(literal.(type))(); separator=", ">}, sizeThree)
+ || Arrays.equals(new <type>[]{<["0", "2", "1"]:(literal.(type))(); separator=", ">}, sizeThree)
+ || Arrays.equals(new <type>[]{<["2", "0", "1"]:(literal.(type))(); separator=", ">}, sizeThree)
+ || Arrays.equals(new <type>[]{<["1", "0", "2"]:(literal.(type))(); separator=", ">}, sizeThree)
+ );
+ <type>[] sizeTwo = iterable.toSizedArray(2);
+ Assert.assertTrue(Arrays.equals(new <type>[]{<["1", "2"]:(literal.(type))(); separator=", ">}, sizeTwo)
+ || Arrays.equals(new <type>[]{<["2", "1"]:(literal.(type))(); separator=", ">}, sizeTwo));
+ <type>[] sizeOne = iterable.toSizedArray(1);
+ Assert.assertTrue(Arrays.equals(new <type>[]{<["1"]:(literal.(type))(); separator=", ">}, sizeOne)
+ || Arrays.equals(new <type>[]{<["2"]:(literal.(type))(); separator=", ">}, sizeOne));
+ <type>[] sizeZero = iterable.toSizedArray(0);
+ Assert.assertTrue(Arrays.equals(new <type>[]{}, sizeZero));
+ }
+
  @Test
  public void toArrayWithTargetArray()
  {

eclipse-collections/src/main/java/org/eclipse/collections/impl/list/immutable/primitive/ImmutableBooleanArrayList.java

@@ -87,6 +87,11 @@ public static ImmutableBooleanArrayList newList(BooleanIterable iterable)
  return new ImmutableBooleanArrayList(iterable.toArray());
  }
 
+ public static ImmutableBooleanArrayList newList(BooleanIterable iterable, int size)
+ {
+ return new ImmutableBooleanArrayList(iterable.toSizedArray(size));
+ }
+
  public static ImmutableBooleanArrayList newListWith(boolean... elements)
  {
  return new ImmutableBooleanArrayList(elements);
@@ -289,8 +294,15 @@ public <V> ImmutableList<V> collect(BooleanToObjectFunction<? extends V> functio
  @Override
  public boolean[] toArray()
  {
- boolean[] newItems = new boolean[this.size];
- for (int i = 0; i < this.size; i++)
+ return this.toSizedArray(this.size);
+ }
+
+ @Override
+ public boolean[] toSizedArray(int s)
+ {
+ boolean[] newItems = new boolean[s];
+ int newSize = Math.min(s, this.size);
+ for (int i = 0; i < newSize; i++)
  {
  newItems[i] = this.items.get(i);
  }

eclipse-collections/src/main/java/org/eclipse/collections/impl/list/mutable/primitive/BooleanArrayList.java

@@ -797,8 +797,15 @@ public <V> MutableList<V> collect(BooleanToObjectFunction<? extends V> function)
  @Override
  public boolean[] toArray()
  {
- boolean[] newItems = new boolean[this.size];
- for (int i = 0; i < this.size; i++)
+ return this.toSizedArray(this.size);
+ }
+
+ @Override
+ public boolean[] toSizedArray(int s)
+ {
+ boolean[] newItems = new boolean[s];
+ int newSize = Math.min(s, this.size);
+ for (int i = 0; i < newSize; i++)
  {
  newItems[i] = this.items.get(i);
  }

unit-tests/src/test/java/org/eclipse/collections/impl/collection/mutable/primitive/AbstractBooleanIterableTestCase.java

@@ -505,6 +505,19 @@ public void toArray()
  || Arrays.equals(new boolean[]{true, false}, this.newWith(true, false).toArray()));
  }
 
+ @Test
+ public void toSizedArray()
+ {
+ assertEquals(0L, this.newWith().toSizedArray(0).length);
+ assertEquals(1L, this.newWith().toSizedArray(1).length);
+ assertEquals(0L, this.newWith(true).toSizedArray(0).length);
+ assertTrue(Arrays.equals(new boolean[]{true}, this.newWith(true).toSizedArray(1)));
+ assertTrue(Arrays.equals(new boolean[]{true, false}, this.newWith(true).toSizedArray(2))
+ || Arrays.equals(new boolean[]{false, true}, this.newWith(true).toSizedArray(2)));
+ assertTrue(Arrays.equals(new boolean[]{false, true}, this.newWith(true, false).toSizedArray(2))
+ || Arrays.equals(new boolean[]{true, false}, this.newWith(true, false).toSizedArray(2)));
+ }
+
  @Test
  public void testEquals()
  {