Fix some PMD issues

Signed-off-by: Taylor Smock <taylor.smock@kaart.com>

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/DataAvailability.java

@@ -29,7 +29,7 @@ public class DataAvailability {
     /** This points to a list of default sources that can be used with MapWithAI */
     public static final String DEFAULT_SERVER_URL = "https://gokaart.gitlab.io/JOSM_MapWithAI/json/sources.json";
     /** A map of tag -> message of possible data types */
-    protected static final Map<String, String> POSSIBLE_DATA_POINTS = new TreeMap<>();
+    static final Map<String, String> POSSIBLE_DATA_POINTS = new TreeMap<>();
 
     private static final String PROVIDES = "provides";
 
@@ -50,7 +50,7 @@ public class DataAvailability {
      * A map of countries to a map of available types
      * ({@code Map<Country, Map<Type, IsAvailable>>}
      */
-    protected static final Map<String, Map<String, Boolean>> COUNTRIES = new HashMap<>();
+    static final Map<String, Map<String, Boolean>> COUNTRIES = new HashMap<>();
 
     private static class InstanceHelper {
         static DataAvailability instance = new DataAvailability();

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/MapWithAIDataUtils.java

@@ -8,14 +8,12 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 import java.util.TreeSet;
 import java.util.concurrent.ForkJoinPool;
 import java.util.concurrent.locks.Lock;
 import java.util.stream.Collectors;
 
-import javax.json.JsonObject;
 import javax.swing.JOptionPane;
 import javax.swing.SwingUtilities;
 

src/main/java/org/openstreetmap/josm/plugins/mapwithai/frontend/MapWithAIDownloadReader.java

@@ -68,7 +68,7 @@ public class MapWithAIDownloadReader implements DownloadSource<MapWithAIDownload
                         .filter(map -> map.getBoolean("enabled", false)).filter(map -> map.containsKey("parameter"))
                         .map(map -> map.getString("parameter")).collect(Collectors.toList());
                 if (!parameters.isEmpty()) {
-                    sb.append("&").append(String.join("&", parameters));
+                    sb.append('&').append(String.join("&", parameters));
                 }
             }
         }