IntelliJ Themes: do not release JSON memory to allow re-using theme instance (issue #1020)

Author: DevCharly

CHANGELOG.md

@@ -32,6 +32,8 @@ FlatLaf Change Log
   modal dialogs. (issue #1048)
 - JideButton, JideToggleButton, JideSplitButton and JideToggleSplitButton: Paint
   border in button style `TOOLBAR_STYLE` if in selected state. (issue #1045)
+- IntelliJ Themes: Fixed problem when using theme instance more than once when
+  switching to that theme. (issue #990)
 
 
 ## 3.6.2

flatlaf-core/src/main/java/com/formdev/flatlaf/IntelliJTheme.java

@@ -58,9 +58,9 @@ public class IntelliJTheme
 	public final boolean dark;
 	public final String author;
 
-	private Map<String, String> jsonColors;
-	private Map<String, Object> jsonUI;
-	private Map<String, Object> jsonIcons;
+	private final Map<String, String> jsonColors;
+	private final Map<String, Object> jsonUI;
+	private final Map<String, Object> jsonIcons;
 
 	private Map<String, String> namedColors = Collections.emptyMap();
 
@@ -276,11 +276,6 @@ private void applyProperties( Properties properties ) {
 
 			put( properties, key, value );
 		}
-
-		// let Java release memory
-		jsonColors = null;
-		jsonUI = null;
-		jsonIcons = null;
 	}
 
 	private String get( Properties properties, Map<String, String> themeSpecificProps, String key ) {