8155600: Performance optimization of Arrays.asList().iterator()

Reviewed-by: redestad, shade, plevart, attila

jdk/src/java.base/share/classes/java/util/Arrays.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -4403,6 +4403,35 @@ public class Arrays {
         public void sort(Comparator<? super E> c) {
             Arrays.sort(a, c);
         }
+
+        @Override
+        public Iterator<E> iterator() {
+            return new ArrayItr<>(a);
+        }
+    }
+
+    private static class ArrayItr<E> implements Iterator<E> {
+        private int cursor;
+        private final E[] a;
+
+        ArrayItr(E[] a) {
+            this.a = a;
+        }
+
+        @Override
+        public boolean hasNext() {
+            return cursor < a.length;
+        }
+
+        @Override
+        public E next() {
+            int i = cursor;
+            if (i >= a.length) {
+                throw new NoSuchElementException();
+            }
+            cursor = i + 1;
+            return a[i];
+        }
     }
 
     /**

jdk/test/java/util/Arrays/AsList.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8155600
+ * @summary Tests for Arrays.asList()
+ * @run testng AsList
+ */
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.stream.IntStream;
+
+import org.testng.annotations.Test;
+import org.testng.annotations.DataProvider;
+import static org.testng.Assert.assertSame;
+import static org.testng.Assert.assertTrue;
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.fail;
+
+public class AsList {
+    /*
+     * Iterator contract test
+     */
+    @Test(dataProvider = "Arrays")
+    public void testIterator(Object[] array) {
+        Iterator<Object> itr = Arrays.asList(array).iterator();
+        for (int i = 0; i < array.length; i++) {
+            assertTrue(itr.hasNext());
+            assertTrue(itr.hasNext()); // must be idempotent
+            assertSame(array[i], itr.next());
+            try {
+                itr.remove();
+                fail("Remove must throw");
+            } catch (UnsupportedOperationException ex) {
+                // expected
+            }
+        }
+        assertFalse(itr.hasNext());
+        for (int i = 0; i < 3; i++) {
+            assertFalse(itr.hasNext());
+            try {
+                itr.next();
+                fail("Next succeed when there's no data left");
+            } catch (NoSuchElementException ex) {
+                // expected
+            }
+        }
+    }
+
+    @DataProvider(name = "Arrays")
+    public static Object[][] arrays() {
+        Object[][] arrays = {
+            { new Object[] { } },
+            { new Object[] { 1 } },
+            { new Object[] { null } },
+            { new Object[] { null, 1 } },
+            { new Object[] { 1, null } },
+            { new Object[] { null, null } },
+            { new Object[] { null, 1, 2 } },
+            { new Object[] { 1, null, 2 } },
+            { new Object[] { 1, 2, null } },
+            { new Object[] { null, null, null } },
+            { new Object[] { 1, 2, 3, null, 4 } },
+            { new Object[] { "a", "a", "a", "a" } },
+            { IntStream.range(0, 100).boxed().toArray() }
+        };
+
+        return arrays;
+    }
+}