8308588: Unnecessary synchronized on GTKStyle#ICONS_MAP can be removed

Reviewed-by: tr, aivanov, aturbanov

Author: Abhishek Kumar

src/java.desktop/share/classes/com/sun/java/swing/plaf/gtk/GTKStyle.java

@@ -888,11 +888,7 @@ else if ("CheckBox.iconTextGap".equals(key) ||
         }
 
         // Is it a stock icon ?
-        GTKStockIcon stockIcon = null;
-        synchronized (ICONS_MAP) {
-            stockIcon = ICONS_MAP.get(key);
-        }
-
+        GTKStockIcon stockIcon = ICONS_MAP.get(key);
         if (stockIcon != null) {
             return stockIcon;
         }
@@ -1179,27 +1175,28 @@ public Object createValue(UIDefaults table) {
         CLASS_SPECIFIC_MAP.put("EditorPane.caretForeground", "cursor-color");
         CLASS_SPECIFIC_MAP.put("EditorPane.caretAspectRatio", "cursor-aspect-ratio");
 
-        ICONS_MAP = new HashMap<String, GTKStockIcon>();
-        ICONS_MAP.put("FileChooser.cancelIcon", new GTKStockIcon("gtk-cancel", 4));
-        ICONS_MAP.put("FileChooser.okIcon",     new GTKStockIcon("gtk-ok",     4));
-        ICONS_MAP.put("OptionPane.yesIcon", new GTKStockIcon("gtk-yes", 4));
-        ICONS_MAP.put("OptionPane.noIcon", new GTKStockIcon("gtk-no", 4));
-        ICONS_MAP.put("OptionPane.cancelIcon", new GTKStockIcon("gtk-cancel", 4));
-        ICONS_MAP.put("OptionPane.okIcon", new GTKStockIcon("gtk-ok", 4));
+        Map<String,GTKStockIcon> iconsMap = new HashMap<>();
+        iconsMap.put("FileChooser.cancelIcon", new GTKStockIcon("gtk-cancel", 4));
+        iconsMap.put("FileChooser.okIcon",     new GTKStockIcon("gtk-ok",     4));
+        iconsMap.put("OptionPane.yesIcon", new GTKStockIcon("gtk-yes", 4));
+        iconsMap.put("OptionPane.noIcon", new GTKStockIcon("gtk-no", 4));
+        iconsMap.put("OptionPane.cancelIcon", new GTKStockIcon("gtk-cancel", 4));
+        iconsMap.put("OptionPane.okIcon", new GTKStockIcon("gtk-ok", 4));
 
         //check whether the gtk version is >= 3.10 as the Icon names were
         //changed from this version
         UNIXToolkit tk = (UNIXToolkit)Toolkit.getDefaultToolkit();
         if (tk.checkGtkVersion(3, 10, 0)) {
-            ICONS_MAP.put("OptionPane.errorIcon", new GTKStockIcon("dialog-error", 6));
-            ICONS_MAP.put("OptionPane.informationIcon", new GTKStockIcon("dialog-information", 6));
-            ICONS_MAP.put("OptionPane.warningIcon", new GTKStockIcon("dialog-warning", 6));
-            ICONS_MAP.put("OptionPane.questionIcon", new GTKStockIcon("dialog-question", 6));
+            iconsMap.put("OptionPane.errorIcon", new GTKStockIcon("dialog-error", 6));
+            iconsMap.put("OptionPane.informationIcon", new GTKStockIcon("dialog-information", 6));
+            iconsMap.put("OptionPane.warningIcon", new GTKStockIcon("dialog-warning", 6));
+            iconsMap.put("OptionPane.questionIcon", new GTKStockIcon("dialog-question", 6));
         } else {
-            ICONS_MAP.put("OptionPane.errorIcon", new GTKStockIcon("gtk-dialog-error", 6));
-            ICONS_MAP.put("OptionPane.informationIcon", new GTKStockIcon("gtk-dialog-info", 6));
-            ICONS_MAP.put("OptionPane.warningIcon", new GTKStockIcon("gtk-dialog-warning", 6));
-            ICONS_MAP.put("OptionPane.questionIcon", new GTKStockIcon("gtk-dialog-question", 6));
+            iconsMap.put("OptionPane.errorIcon", new GTKStockIcon("gtk-dialog-error", 6));
+            iconsMap.put("OptionPane.informationIcon", new GTKStockIcon("gtk-dialog-info", 6));
+            iconsMap.put("OptionPane.warningIcon", new GTKStockIcon("gtk-dialog-warning", 6));
+            iconsMap.put("OptionPane.questionIcon", new GTKStockIcon("gtk-dialog-question", 6));
         }
+        ICONS_MAP = Collections.unmodifiableMap(iconsMap);
     }
 }