8189319: Add a java.util.Properties constructor that takes an initial capacity

Reviewed-by: martin, mchung, rriggs

src/java.base/share/classes/java/lang/System.java

@@ -1937,7 +1937,7 @@ public final class System {
         // initialization. So make sure the "props" is available at the
         // very beginning of the initialization and all system properties to
         // be put into it directly.
-        props = new Properties();
+        props = new Properties(84);
         initProperties(props);  // initialized by the VM
 
         // There are certain system configurations that may be controlled by

src/java.base/share/classes/java/util/Properties.java

@@ -122,6 +122,10 @@ import jdk.internal.util.xml.PropertiesDefaultHandler;
  * <p>This class is thread-safe: multiple threads can share a single
  * {@code Properties} object without the need for external synchronization.
  *
+ * @apiNote
+ * The {@code Properties} class does not inherit the concept of a load factor
+ * from its superclass, {@code Hashtable}.
+ *
  * @author  Arthur van Hoff
  * @author  Michael McCloskey
  * @author  Xueming Shen
@@ -148,25 +152,49 @@ class Properties extends Hashtable<Object,Object> {
      * simple read operations.  Writes and bulk operations remain synchronized,
      * as in Hashtable.
      */
-    private transient ConcurrentHashMap<Object, Object> map =
+    private transient ConcurrentHashMap<Object, Object> map;
-            new ConcurrentHashMap<>(8);
 
     /**
      * Creates an empty property list with no default values.
+     *
+     * @implNote The initial capacity of a {@code Properties} object created
+     * with this constructor is unspecified.
      */
     public Properties() {
-        this(null);
+        this(null, 8);
+    }
+
+    /**
+     * Creates an empty property list with no default values, and with an
+     * initial size accommodating the specified number of elements without the
+     * need to dynamically resize.
+     *
+     * @param  initialCapacity the {@code Properties} will be sized to
+     *         accommodate this many elements
+     * @throws IllegalArgumentException if the initial capacity is less than
+     *         zero.
+     */
+    public Properties(int initialCapacity) {
+        this(null, initialCapacity);
     }
 
     /**
      * Creates an empty property list with the specified defaults.
      *
+     * @implNote The initial capacity of a {@code Properties} object created
+     * with this constructor is unspecified.
+     *
      * @param   defaults   the defaults.
      */
     public Properties(Properties defaults) {
+        this(defaults, 8);
+    }
+
+    private Properties(Properties defaults, int initialCapacity) {
         // use package-private constructor to
         // initialize unused fields with dummy values
         super((Void) null);
+        map = new ConcurrentHashMap<>(initialCapacity);
         this.defaults = defaults;
     }
 

test/jdk/java/util/Properties/InitialCapacity.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2017, 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.
+ */
+
+import java.util.Properties;
+import org.testng.annotations.Test;
+
+/*
+ * @test
+ * @bug 8189319
+ * @summary Test that Properties(int initialCapacity) throws exceptions (or
+            doesn't) as expected
+ * @run testng InitialCapacity
+ */
+public class InitialCapacity {
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void negativeInitCap() { Properties p = new Properties(-1); }
+
+    @Test
+    public void positiveInitCap() { Properties p = new Properties(10); }
+}