Generated default implementations for Collection.toArray().

#KT-3352 in progress

runtime/src/jet/runtime/CollectionToArray.java

@@ -0,0 +1,63 @@
+package jet.runtime;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Iterator;
+
+public class CollectionToArray {
+    // Implementation copied from AbstractCollection
+
+    public static Object[] toArray(Collection<?> collection) {
+        Object[] r = new Object[collection.size()];
+        Iterator<?> it = collection.iterator();
+        for (int i = 0; i < r.length; i++) {
+            if (! it.hasNext())	// fewer elements than expected
+                return Arrays.copyOf(r, i);
+            r[i] = it.next();
+        }
+        return it.hasNext() ? finishToArray(r, it) : r;
+    }
+
+    public static <T, E> T[] toArray(Collection<E> collection, T[] a) {
+        // Estimate size of array; be prepared to see more or fewer elements
+        int size = collection.size();
+        T[] r = a.length >= size ? a :
+                (T[])java.lang.reflect.Array
+                        .newInstance(a.getClass().getComponentType(), size);
+        Iterator<E> it = collection.iterator();
+
+        for (int i = 0; i < r.length; i++) {
+            if (! it.hasNext()) { // fewer elements than expected
+                if (a != r)
+                    return Arrays.copyOf(r, i);
+                r[i] = null; // null-terminate
+                return r;
+            }
+            r[i] = (T)it.next();
+        }
+        return it.hasNext() ? finishToArray(r, it) : r;
+    }
+
+    private static <T> T[] finishToArray(T[] r, Iterator<?> it) {
+        int i = r.length;
+        while (it.hasNext()) {
+            int cap = r.length;
+            if (i == cap) {
+                int newCap = ((cap / 2) + 1) * 3;
+                if (newCap <= cap) { // integer overflow
+                    if (cap == Integer.MAX_VALUE)
+                        throw new OutOfMemoryError
+                                ("Required array size too large");
+                    newCap = Integer.MAX_VALUE;
+                }
+                r = Arrays.copyOf(r, newCap);
+            }
+            r[i++] = (T)it.next();
+        }
+        // trim if overallocated
+        return (i == r.length) ? r : Arrays.copyOf(r, i);
+    }
+
+    private CollectionToArray() {
+    }
+}