Fix SpotBugs SBSC_USE_STRINGBUFFER_CONCATENATION warnings

Refactored code to use StringBuilder in loops to prevent string concatenation performance issues.
Updated .github/scripts/generate-quality-report.py to treat SBSC_USE_STRINGBUFFER_CONCATENATION as a build failure.

Author: google-labs-jules[bot]

CodenameOne/src/com/codename1/ui/html/HTMLComponent.java

@@ -2223,17 +2223,17 @@ private Label addString(String str, int align) {
                         int spacesToAdd = (width - lbl.getPreferredW()) / spaceW;
                         int spacesPerWord = spacesToAdd / (words.size() - 1);
                         int addtlSpaces = spacesToAdd % (words.size() - 1);
-                        String newStr = (String) words.elementAt(0);
+                        StringBuilder newStr = new StringBuilder((String) words.elementAt(0));
                         for (int i = 1; i < words.size(); i++) {
                             for (int j = 0; j < spacesPerWord; j++) {
-                                newStr += ' ';
+                                newStr.append(' ');
                             }
                             if (i - 1 < addtlSpaces) {
-                                newStr += ' ';
+                                newStr.append(' ');
                             }
-                            newStr += ' ' + (String) words.elementAt(i);
+                            newStr.append(' ').append((String) words.elementAt(i));
                         }
-                        lbl.setText(newStr);
+                        lbl.setText(newStr.toString());
                     }
                 } else {
                     lbl.setPreferredW(width);

CodenameOne/src/com/codename1/ui/html/HTMLElement.java

@@ -971,11 +971,11 @@ static int getColor(String colorStr, int defaultColor) {
         }
 
         if (colorStr.length() == 3) { // shortened format rgb - translated to rrggbb
-            String newColStr = "";
+            StringBuilder newColStr = new StringBuilder();
             for (int i = 0; i < 3; i++) {
-                newColStr += colorStr.charAt(i) + "" + colorStr.charAt(i);
+                newColStr.append(colorStr.charAt(i)).append("").append(colorStr.charAt(i));
             }
-            colorStr = newColStr;
+            colorStr = newColStr.toString();
         }
 
         try {
@@ -1159,23 +1159,23 @@ public String getSupportedAttributesList() {
         if ((id < 0) || (id >= TAG_ATTRIBUTES.length)) {
             return "Unknown";
         }
-        String list = "";
+        StringBuilder list = new StringBuilder();
         for (int a = 0; a < TAG_ATTRIBUTES[id].length; a++) {
-            list += ATTRIBUTE_NAMES[TAG_ATTRIBUTES[id][a]] + ",";
+            list.append(ATTRIBUTE_NAMES[TAG_ATTRIBUTES[id][a]]).append(",");
         }
         if (supportsCoreAttributes()) {
             for (int a = 0; a < COMMON_ATTRIBUTES.length; a++) {
-                list += ATTRIBUTE_NAMES[COMMON_ATTRIBUTES[a]] + ",";
+                list.append(ATTRIBUTE_NAMES[COMMON_ATTRIBUTES[a]]).append(",");
             }
         }
 
-        if (list.endsWith(",")) {
-            list = list.substring(0, list.length() - 1);
+        if (list.length() > 0 && list.charAt(list.length() - 1) == ',') {
+            list.setLength(list.length() - 1);
         }
-        if (list.equals("")) {
-            list = "None";
+        if (list.length() == 0) {
+            return "None";
         }
-        return list;
+        return list.toString();
     }
 
     /**