Fix SpotBugs SS_SHOULD_BE_STATIC warnings (#4380)

* Fix SpotBugs "Unread field: should this field be static?" warnings

Converted identified fields to static final constants where appropriate and removed unused fields in:
- CacheMap.java
- JavascriptContext.java
- MapComponent.java
- ArrowLinesLayer.java
- Component.java
- FlipTransition.java
- LookAndFeel.java
- DateSpinner3D.java
- Spinner3D.java
- SpinnerNode.java
- Tree.java
- CodenameOneMiGComponentWrapper.java
- MigLayout.java

Updated maven/core-unittests/pom.xml to fail on SpotBugs errors.

* Fix SpotBugs "Unread field: should this field be static?" warnings

Converted identified fields to static final constants where appropriate and removed unused fields in:
- CacheMap.java
- JavascriptContext.java
- MapComponent.java
- ArrowLinesLayer.java
- Component.java
- FlipTransition.java
- LookAndFeel.java
- DateSpinner3D.java
- Spinner3D.java
- SpinnerNode.java
- Tree.java
- CodenameOneMiGComponentWrapper.java
- MigLayout.java

Updated maven/core-unittests/pom.xml to fail on SpotBugs errors.
Updated .github/scripts/generate-quality-report.py to fail on SS_SHOULD_BE_STATIC.

* Fix SpotBugs "Unread field: should this field be static?" warnings

Converted identified fields to static final constants where appropriate and removed unused fields in:
- CacheMap.java
- JavascriptContext.java
- MapComponent.java
- ArrowLinesLayer.java
- Component.java
- FlipTransition.java
- LookAndFeel.java
- DateSpinner3D.java
- Spinner3D.java
- SpinnerNode.java
- Tree.java
- CodenameOneMiGComponentWrapper.java
- MigLayout.java

Updated maven/core-unittests/pom.xml to fail on SpotBugs errors.
Updated .github/scripts/generate-quality-report.py to fail on SS_SHOULD_BE_STATIC.

* Fix SpotBugs SS_SHOULD_BE_STATIC warnings and enforce build failure

Refactored several fields to be `static final` where appropriate to address "Unread field: should this field be static?" warnings. Removed unused fields in `MigLayout`, `CacheMap`, and `CodenameOneMiGComponentWrapper`.
Updated `maven/core-unittests/pom.xml` to fail on error and `.github/scripts/generate-quality-report.py` to forbid `SS_SHOULD_BE_STATIC`.

Modified files:
- `CodenameOne/src/com/codename1/io/CacheMap.java`
- `CodenameOne/src/com/codename1/javascript/JavascriptContext.java`
- `CodenameOne/src/com/codename1/maps/MapComponent.java`
- `CodenameOne/src/com/codename1/maps/layers/ArrowLinesLayer.java`
- `CodenameOne/src/com/codename1/ui/Component.java`
- `CodenameOne/src/com/codename1/ui/animations/FlipTransition.java`
- `CodenameOne/src/com/codename1/ui/layouts/mig/CodenameOneMiGComponentWrapper.java`
- `CodenameOne/src/com/codename1/ui/layouts/mig/MigLayout.java`
- `CodenameOne/src/com/codename1/ui/plaf/LookAndFeel.java`
- `CodenameOne/src/com/codename1/ui/spinner/DateSpinner3D.java`
- `CodenameOne/src/com/codename1/ui/spinner/SpinnerNode.java`
- `CodenameOne/src/com/codename1/ui/tree/Tree.java`
- `maven/core-unittests/pom.xml`
- `.github/scripts/generate-quality-report.py`

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: google-labs-jules[bot]

.github/scripts/generate-quality-report.py

@@ -808,7 +808,8 @@ def main() -> None:
             "UI_INHERITANCE_UNSAFE_GETRESOURCE",
             "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD",
             "UW_UNCOND_WAIT",
-            "SIC_INNER_SHOULD_BE_STATIC_ANON"
+            "SIC_INNER_SHOULD_BE_STATIC_ANON",
+            "SS_SHOULD_BE_STATIC"
         }
 
         def _is_exempt(f: Finding) -> bool:

CodenameOne/src/com/codename1/io/CacheMap.java

@@ -50,7 +50,6 @@ public class CacheMap {
     private Vector storageCacheContentVec;
     private String cachePrefix = "";
     private boolean alwaysStore;
-    private final int storageKey = -1;
 
     /**
      * Default constructor

CodenameOne/src/com/codename1/javascript/JavascriptContext.java

@@ -144,9 +144,9 @@ public class JavascriptContext {
      * Whenever the objectMap exceeds this size, cleanup will be called whenever retain()
      * is called.
      */
-    private final int objectMapThresholdSize = 500;
+    private static final int objectMapThresholdSize = 500;
     private final Random cleanupRandomizer = new Random();
-    private final double cleanupProbability = 0.1;
+    private static final double cleanupProbability = 0.1;
     private JSObject window;
 
     /**

CodenameOne/src/com/codename1/maps/MapComponent.java

@@ -82,8 +82,8 @@ public class MapComponent extends Container {
     private int zoomCenterY = 0;
     private long lastPressed = -1;
     private int tapCount = 0;
-    private final int singleTapThreshold = 200;
-    private final int doubleTapThreshold = 200;
+    private static final int singleTapThreshold = 200;
+    private static final int doubleTapThreshold = 200;
     private ArrayList<MapListener> listeners;
 
     /**

CodenameOne/src/com/codename1/maps/layers/ArrowLinesLayer.java

@@ -35,7 +35,7 @@
  */
 public class ArrowLinesLayer extends LinesLayer {
 
-    private final int minArrowSementLength = 20;
+    private static final int minArrowSementLength = 20;
     private int arrowSegmentLength = 60;
     private int arrowWidth = 5;
     private int arrowHeight = 10;

CodenameOne/src/com/codename1/ui/Component.java

@@ -321,7 +321,7 @@ public class Component implements Animation, StyleListener, Editable {
      * is too slow to be useful.  This may not be the case on other platforms, but, for now, we'll leave this flag on.
      * Later on, after evaluation, this flag will likely be removed, and the best strategy will be decided upon.
      */
-    private final boolean useLightweightElevationShadow = true;
+    private static final boolean useLightweightElevationShadow = true;
     /**
      * This property is useful for blocking in z-order touch events, sometimes we might want to grab touch events in
      * a specific component without making it focusable.

CodenameOne/src/com/codename1/ui/animations/FlipTransition.java

@@ -62,8 +62,8 @@ public class FlipTransition extends Transition {
     private int transitionState = STATE_MOVE_AWAY;
 
     private Motion motion;
-    private final boolean firstFinished = false;
-    private final boolean started = false;
+    private static final boolean firstFinished = false;
+    private static final boolean started = false;
 
     private int bgColor = -1;
 

CodenameOne/src/com/codename1/ui/layouts/mig/CodenameOneMiGComponentWrapper.java

@@ -77,7 +77,6 @@ class CodenameOneMiGComponentWrapper implements ComponentWrapper {
     private final Component c;
     private int compType = TYPE_UNSET;
     private final Boolean bl = null;
-    private final boolean prefCalled = false;
 
     public CodenameOneMiGComponentWrapper(Component c) {
         this.c = c;

CodenameOne/src/com/codename1/ui/layouts/mig/MigLayout.java

@@ -83,7 +83,6 @@ public final class MigLayout extends Layout {
     private ArrayList<LayoutCallback> callbackList = null;
 
     private boolean dirty = true;
-    private final long lastSize = 0;
 
     /**
      * Constructor with no constraints.

CodenameOne/src/com/codename1/ui/plaf/LookAndFeel.java

@@ -130,8 +130,8 @@ public abstract class LookAndFeel {
     private Image fadeScrollBottom;
     private Image fadeScrollRight;
     private Image fadeScrollLeft;
-    private final int fadeScrollEdgeStartAlpha = 0x999999;
-    private final int fadeScrollEdgeEndAlpha = 0;
+    private static final int fadeScrollEdgeStartAlpha = 0x999999;
+    private static final int fadeScrollEdgeEndAlpha = 0;
     private int textFieldCursorColor;
 
     private boolean backgroundImageDetermineSize;