--- a/src/java.base/share/classes/java/lang/System.java	Wed Dec 12 15:26:49 2018 +0300
+++ b/src/java.base/share/classes/java/lang/System.java	Wed Dec 12 13:28:50 2018 +0100
@@ -801,8 +801,9 @@
         }
 
         if (props == null) {
-            props = SystemProps.initProperties();
-            VersionProps.init(props);
+            Map<String, String> tempProps = SystemProps.initProperties();
+            VersionProps.init(tempProps);
+            props = createProperties(tempProps);
         }
         System.props = props;
     }
@@ -1960,17 +1961,41 @@
     }
 
     /**
+     * Create the Properties object from a map - masking out system properties
+     * that are not intended for public access.
+     */
+    private static Properties createProperties(Map<String, String> initialProps) {
+        Properties properties = new Properties(initialProps.size());
+        for (var entry : initialProps.entrySet()) {
+            String prop = entry.getKey();
+            switch (prop) {
+                // Do not add private system properties to the Properties
+                case "sun.nio.MaxDirectMemorySize":
+                case "sun.nio.PageAlignDirectMemory":
+                    // used by java.lang.Integer.IntegerCache
+                case "java.lang.Integer.IntegerCache.high":
+                    // used by sun.launcher.LauncherHelper
+                case "sun.java.launcher.diag":
+                    // used by jdk.internal.loader.ClassLoaders
+                case "jdk.boot.class.path.append":
+                    break;
+                default:
+                    properties.put(prop, entry.getValue());
+            }
+        }
+        return properties;
+    }
+
+    /**
      * Initialize the system class.  Called after thread initialization.
      */
     private static void initPhase1() {
-
         // VM might invoke JNU_NewStringPlatform() to set those encoding
         // sensitive properties (user.home, user.name, boot.class.path, etc.)
         // during "props" initialization.
         // The charset is initialized in System.c and does not depend on the Properties.
-        props = SystemProps.initProperties();
-        VersionProps.init(props);
-        StaticProperty.javaHome();          // Load StaticProperty to cache the property values
+        Map<String, String> tempProps = SystemProps.initProperties();
+        VersionProps.init(tempProps);
 
         // There are certain system configurations that may be controlled by
         // VM options such as the maximum amount of direct memory and
@@ -1978,15 +2003,14 @@
         // of autoboxing.  Typically, the library will obtain these values
         // from the properties set by the VM.  If the properties are for
         // internal implementation use only, these properties should be
-        // removed from the system properties.
-        //
-        // See java.lang.Integer.IntegerCache and the
-        // VM.saveAndRemoveProperties method for example.
+        // masked from the system properties.
         //
         // Save a private copy of the system properties object that
-        // can only be accessed by the internal implementation.  Remove
-        // certain system properties that are not intended for public access.
-        VM.saveAndRemoveProperties(props);
+        // can only be accessed by the internal implementation.
+        VM.saveProperties(tempProps);
+        props = createProperties(tempProps);
+
+        StaticProperty.javaHome();          // Load StaticProperty to cache the property values
 
         lineSeparator = props.getProperty("line.separator");
 

--- a/src/java.base/share/classes/java/lang/VersionProps.java.template	Wed Dec 12 15:26:49 2018 +0300
+++ b/src/java.base/share/classes/java/lang/VersionProps.java.template	Wed Dec 12 13:28:50 2018 +0100
@@ -28,8 +28,8 @@
 import java.io.PrintStream;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
-import java.util.Properties;
 
 class VersionProps {
 
@@ -88,25 +88,25 @@
     /**
      * Initialize system properties using build provided values.
      *
-     * @param props Properties instance in which to insert the properties
+     * @param props Map instance in which to insert the properties
      */
-    public static void init(Properties props) {
-        props.setProperty("java.version", java_version);
-        props.setProperty("java.version.date", java_version_date);
-        props.setProperty("java.runtime.version", java_runtime_version);
-        props.setProperty("java.runtime.name", java_runtime_name);
+    public static void init(Map<String, String> props) {
+        props.put("java.version", java_version);
+        props.put("java.version.date", java_version_date);
+        props.put("java.runtime.version", java_runtime_version);
+        props.put("java.runtime.name", java_runtime_name);
         if (VENDOR_VERSION_STRING.length() > 0)
-            props.setProperty("java.vendor.version", VENDOR_VERSION_STRING);
+            props.put("java.vendor.version", VENDOR_VERSION_STRING);
 
-        props.setProperty("java.class.version", CLASSFILE_MAJOR_MINOR);
+        props.put("java.class.version", CLASSFILE_MAJOR_MINOR);
 
-        props.setProperty("java.specification.version", VERSION_SPECIFICATION);
-        props.setProperty("java.specification.name", "Java Platform API Specification");
-        props.setProperty("java.specification.vendor", "Oracle Corporation");
+        props.put("java.specification.version", VERSION_SPECIFICATION);
+        props.put("java.specification.name", "Java Platform API Specification");
+        props.put("java.specification.vendor", "Oracle Corporation");
 
-        props.setProperty("java.vendor", VENDOR);
-        props.setProperty("java.vendor.url", VENDOR_URL);
-        props.setProperty("java.vendor.url.bug", VENDOR_URL_BUG);
+        props.put("java.vendor", VENDOR);
+        props.put("java.vendor.url", VENDOR_URL);
+        props.put("java.vendor.url.bug", VENDOR_URL_BUG);
     }
 
     private static int parseVersionNumber(String version, int prevIndex, int index) {

--- a/src/java.base/share/classes/jdk/internal/misc/VM.java	Wed Dec 12 15:26:49 2018 +0300
+++ b/src/java.base/share/classes/jdk/internal/misc/VM.java	Wed Dec 12 13:28:50 2018 +0100
@@ -26,6 +26,8 @@
 package jdk.internal.misc;
 
 import static java.lang.Thread.State.*;
+
+import java.util.Collections;
 import java.util.Map;
 import java.util.Properties;
 
@@ -175,7 +177,7 @@
         if (savedProps == null)
             throw new IllegalStateException("Not yet initialized");
 
-        return savedProps;
+        return Collections.unmodifiableMap(savedProps);
     }
 
     private static Map<String, String> savedProps;
@@ -184,16 +186,15 @@
     // the system properties that are not intended for public access.
     //
     // This method can only be invoked during system initialization.
-    public static void saveAndRemoveProperties(Properties props) {
+    public static void saveProperties(Map<String, String> props) {
         if (initLevel() != 0)
             throw new IllegalStateException("Wrong init level");
 
-        @SuppressWarnings({"rawtypes", "unchecked"})
-        Map<String, String> sp =
-            Map.ofEntries(props.entrySet().toArray(new Map.Entry[0]));
         // only main thread is running at this time, so savedProps and
         // its content will be correctly published to threads started later
-        savedProps = sp;
+        if (savedProps == null) {
+            savedProps = props;
+        }
 
         // Set the maximum amount of direct memory.  This value is controlled
         // by the vm option -XX:MaxDirectMemorySize=<size>.
@@ -201,7 +202,7 @@
         // from the system property sun.nio.MaxDirectMemorySize set by the VM.
         // If not set or set to -1, the max memory will be used
         // The system property will be removed.
-        String s = (String)props.remove("sun.nio.MaxDirectMemorySize");
+        String s = props.get("sun.nio.MaxDirectMemorySize");
         if (s == null || s.isEmpty() || s.equals("-1")) {
             // -XX:MaxDirectMemorySize not given, take default
             directMemory = Runtime.getRuntime().maxMemory();
@@ -212,19 +213,9 @@
         }
 
         // Check if direct buffers should be page aligned
-        s = (String)props.remove("sun.nio.PageAlignDirectMemory");
+        s = props.get("sun.nio.PageAlignDirectMemory");
         if ("true".equals(s))
             pageAlignDirectMemory = true;
-
-        // Remove other private system properties
-        // used by java.lang.Integer.IntegerCache
-        props.remove("java.lang.Integer.IntegerCache.high");
-
-        // used by sun.launcher.LauncherHelper
-        props.remove("sun.java.launcher.diag");
-
-        // used by jdk.internal.loader.ClassLoaders
-        props.remove("jdk.boot.class.path.append");
     }
 
     // Initialize any miscellaneous operating system settings that need to be

--- a/src/java.base/share/classes/jdk/internal/util/SystemProps.java	Wed Dec 12 15:26:49 2018 +0300
+++ b/src/java.base/share/classes/jdk/internal/util/SystemProps.java	Wed Dec 12 13:28:50 2018 +0100
@@ -26,7 +26,8 @@
 
 
 import java.lang.annotation.Native;
-import java.util.Properties;
+import java.util.HashMap;
+import java.util.Map;
 
 /**
  * System Property initialization for internal use only
@@ -47,12 +48,13 @@
      *
      * @return a Properties instance initialized with all of the properties
      */
-    public static Properties initProperties() {
+    public static Map<String, String> initProperties() {
+
         // Initially, cmdProperties only includes -D and props from the VM
         Raw raw = new Raw();
-        Properties props = raw.cmdProperties();
+        HashMap<String, String> props = raw.cmdProperties();
 
-        String javaHome = props.getProperty("java.home");
+        String javaHome = props.get("java.home");
         assert javaHome != null : "java.home not set";
 
         putIfAbsent(props, "user.home", raw.propDefault(Raw._user_home_NDX));
@@ -120,7 +122,7 @@
      * @param key the key
      * @param value the value
      */
-    private static void put(Properties props, String key, String value) {
+    private static void put(HashMap<String, String> props, String key, String value) {
         if (value != null) {
             props.put(key, value);
         }
@@ -132,7 +134,7 @@
      * @param key the key
      * @param value the value
      */
-    private static void putIfAbsent(Properties props, String key, String value) {
+    private static void putIfAbsent(HashMap<String, String> props, String key, String value) {
         if (value != null) {
             props.putIfAbsent(key, value);
         }
@@ -147,10 +149,12 @@
      * @param display the display value for the base
      * @param format the format value for the base
      */
-    private static void fillI18nProps(Properties cmdProps, String base, String display,
+    private static void fillI18nProps(HashMap<String, String> cmdProps,
+                                      String base,
+                                      String display,
                                       String format) {
         // Do not override command line setting
-        String baseValue = cmdProps.getProperty(base);
+        String baseValue = cmdProps.get(base);
         if (baseValue != null) {
             return;     // Do not override value from the command line
         }
@@ -163,7 +167,7 @@
 
         /* user.xxx.display property */
         String disp = base.concat(".display");
-        String dispValue = cmdProps.getProperty(disp);
+        String dispValue = cmdProps.get(disp);
         if (dispValue == null && display != null && !display.equals(baseValue)) {
             // Create the property only if different from the base property
             cmdProps.put(disp, display);
@@ -171,7 +175,7 @@
 
         /* user.xxx.format property */
         String fmt = base.concat(".format");
-        String fmtValue = cmdProps.getProperty(fmt);
+        String fmtValue = cmdProps.get(fmt);
         if (fmtValue == null && format != null && !format.equals(baseValue)) {
             // Create the property only if different than the base property
             cmdProps.put(fmt, format);
@@ -253,15 +257,17 @@
          *
          * @return return a Properties instance of the command line and VM options
          */
-        private Properties cmdProperties() {
+        private HashMap<String, String> cmdProperties() {
             String[] vmProps = vmProperties();
-            int nProps = vmProps.length / 2;
-            var cmdProps = new Properties(nProps + Raw.FIXED_LENGTH);
-            for (int i = 0; i < nProps; i++) {
-                String k = vmProps[i * 2];
+            // While optimal initialCapacity here would be the exact number of properties
+            // divided by LOAD_FACTOR, a large portion of the properties in Raw are
+            // usually not set, so for typical cases the chosen capacity avoids resizing
+            var cmdProps = new HashMap<String, String>((vmProps.length / 2) + Raw.FIXED_LENGTH);
+            for (int i = 0; i < vmProps.length;) {
+                String k = vmProps[i++];
                 if (k != null) {
-                    String v = vmProps[i * 2 + 1];
-                    cmdProps.setProperty(k, v != null ? v : "");
+                    String v = vmProps[i++];
+                    cmdProps.put(k, v != null ? v : "");
                 } else {
                     // no more key/value pairs
                     break;