Replace things like size == 0 with isEmpty

airsonic-main/src/main/java/org/airsonic/player/controller/MoreController.java

@@ -67,7 +67,7 @@ public class MoreController  {
 
         String uploadDirectory = null;
         List<MusicFolder> musicFolders = settingsService.getMusicFoldersForUser(user.getUsername());
-        if (musicFolders.size() > 0) {
+        if (!musicFolders.isEmpty()) {
             uploadDirectory = new File(musicFolders.get(0).getPath(), "Incoming").getPath();
         }
 

airsonic-main/src/main/java/org/airsonic/player/controller/UploadController.java

@@ -122,7 +122,7 @@ public class UploadController {
 
                 if (!item.isFormField()) {
                     String fileName = item.getName();
-                    if (fileName.trim().length() > 0) {
+                    if (!fileName.trim().isEmpty()) {
 
                         File targetFile = new File(dir, new File(fileName).getName());
 

airsonic-main/src/main/java/org/airsonic/player/security/JWTAuthenticationProvider.java

@@ -78,8 +78,8 @@ public class JWTAuthenticationProvider implements AuthenticationProvider {
             MapDifference<String, List<String>> difference = Maps.difference(expected.getQueryParams(),
                     requested.getQueryParams());
 
-            if(difference.entriesDiffering().size() != 0 ||
-                    difference.entriesOnlyOnLeft().size() != 0 ||
+            if(!difference.entriesDiffering().isEmpty() ||
+                    !difference.entriesOnlyOnLeft().isEmpty() ||
                     difference.entriesOnlyOnRight().size() != 1 ||
                     difference.entriesOnlyOnRight().get(JWTSecurityService.JWT_PARAM_NAME) == null) {
                 logger.debug("False: expected query params [{}] do not match requested query params [{}]", expected.getQueryParams(), requested.getQueryParams());

airsonic-main/src/main/java/org/airsonic/player/service/SettingsService.java

@@ -764,7 +764,7 @@ public class SettingsService {
     }
 
     private void compileExcludePattern() {
-        if (getExcludePatternString() != null && getExcludePatternString().trim().length() > 0) {
+        if (getExcludePatternString() != null && !getExcludePatternString().trim().isEmpty()) {
             excludePattern = Pattern.compile(getExcludePatternString());
         } else {
             excludePattern = null;

airsonic-main/src/main/java/org/airsonic/player/service/metadata/MetaDataParser.java

@@ -164,6 +164,6 @@ public abstract class MetaDataParser {
         }
 
         String result = title.replaceFirst("^\\d{2}[. -]+", "");
-        return result.length() == 0 ? title : result;
+        return result.isEmpty() ? title : result;
     }
 }

airsonic-main/src/main/java/org/airsonic/player/util/StringUtil.java

@@ -285,7 +285,7 @@ public final class StringUtil {
             List<String> result = new ArrayList<String>();
             for (String line = reader.readLine(); line != null; line = reader.readLine()) {
                 line = line.trim();
-                if (!line.startsWith("#") && line.length() > 0) {
+                if (!line.startsWith("#") && !line.isEmpty()) {
                     result.add(line);
                 }
             }

airsonic-main/src/main/java/org/airsonic/player/util/Util.java

@@ -132,7 +132,7 @@ public final class Util {
     public static String getURLForRequest(HttpServletRequest request) {
         String url = request.getRequestURL().toString();
         String queryString = request.getQueryString();
-        if (queryString != null && queryString.length() > 0) url += "?" + queryString;
+        if (queryString != null && !queryString.isEmpty()) url += "?" + queryString;
         return url;
     }
 

airsonic-main/src/main/java/org/airsonic/player/validator/PasswordSettingsValidator.java

@@ -40,7 +40,7 @@ public class PasswordSettingsValidator implements Validator {
     public void validate(Object obj, Errors errors) {
         PasswordSettingsCommand command = (PasswordSettingsCommand) obj;
 
-        if (command.getPassword() == null || command.getPassword().length() == 0) {
+        if (command.getPassword() == null || command.getPassword().isEmpty()) {
             errors.rejectValue("password", "usersettings.nopassword");
         } else if (!command.getPassword().equals(command.getConfirmPassword())) {
             errors.rejectValue("password", "usersettings.wrongpassword");

airsonic-main/src/main/java/org/airsonic/player/validator/UserSettingsValidator.java

@@ -60,7 +60,7 @@ public class UserSettingsValidator implements Validator {
         String confirmPassword = command.getConfirmPassword();
 
         if (command.isNewUser()) {
-            if (username == null || username.length() == 0) {
+            if (username == null || username.isEmpty()) {
                 errors.rejectValue("username", "usersettings.nousername");
             } else if (securityService.getUserByName(username) != null) {
                 errors.rejectValue("username", "usersettings.useralreadyexists");