Migrated the following files in util module to Kotlin

- AbstractTextWatcher
- ActivityUtils
- CommonsDateUtil
- DateUtil

app/src/main/java/fr/free/nrw/commons/campaigns/CampaignView.java

@@ -12,15 +12,15 @@ import androidx.annotation.Nullable;
 import fr.free.nrw.commons.campaigns.models.Campaign;
 import fr.free.nrw.commons.databinding.LayoutCampaginBinding;
 import fr.free.nrw.commons.theme.BaseActivity;
-import fr.free.nrw.commons.utils.DateUtil;
+import fr.free.nrw.commons.utils.CommonsDateUtil;
 
+import fr.free.nrw.commons.utils.DateUtil;
 import java.text.ParseException;
 import java.util.Date;
 
 import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.Utils;
 import fr.free.nrw.commons.contributions.MainActivity;
-import fr.free.nrw.commons.utils.CommonsDateUtil;
 import fr.free.nrw.commons.utils.SwipableCardView;
 import fr.free.nrw.commons.utils.ViewUtil;
 

app/src/main/java/fr/free/nrw/commons/campaigns/CampaignsPresenter.java

@@ -3,6 +3,7 @@ package fr.free.nrw.commons.campaigns;
 import android.annotation.SuppressLint;
 
 import fr.free.nrw.commons.campaigns.models.Campaign;
+import fr.free.nrw.commons.utils.CommonsDateUtil;
 import java.text.ParseException;
 import java.util.Collections;
 import java.util.Date;
@@ -14,7 +15,6 @@ import javax.inject.Singleton;
 
 import fr.free.nrw.commons.BasePresenter;
 import fr.free.nrw.commons.mwapi.OkHttpJsonApiClient;
-import fr.free.nrw.commons.utils.CommonsDateUtil;
 import io.reactivex.Scheduler;
 import io.reactivex.Single;
 import io.reactivex.SingleObserver;

app/src/main/java/fr/free/nrw/commons/delete/ReasonBuilder.java

@@ -3,7 +3,6 @@ package fr.free.nrw.commons.delete;
 import android.content.Context;
 
 import fr.free.nrw.commons.utils.DateUtil;
-
 import java.util.Date;
 import java.util.Locale;
 

app/src/main/java/fr/free/nrw/commons/explore/ExploreFragment.java

@@ -11,7 +11,6 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.viewpager.widget.ViewPager.OnPageChangeListener;
-import com.google.android.material.tabs.TabLayout;
 import fr.free.nrw.commons.R;
 import fr.free.nrw.commons.ViewPagerAdapter;
 import fr.free.nrw.commons.contributions.MainActivity;

app/src/main/java/fr/free/nrw/commons/media/MediaDetailFragment.java

@@ -55,7 +55,6 @@ import fr.free.nrw.commons.Utils;
 import fr.free.nrw.commons.actions.ThanksClient;
 import fr.free.nrw.commons.auth.AccountUtil;
 import fr.free.nrw.commons.auth.SessionManager;
-import fr.free.nrw.commons.auth.csrf.CsrfTokenClient;
 import fr.free.nrw.commons.auth.csrf.InvalidLoginTokenException;
 import fr.free.nrw.commons.category.CategoryClient;
 import fr.free.nrw.commons.category.CategoryDetailsActivity;

app/src/main/java/fr/free/nrw/commons/upload/UploadMediaDetailAdapter.java

@@ -22,7 +22,6 @@ import android.widget.ListView;
 import android.widget.TextView;
 import androidx.activity.result.ActivityResultLauncher;
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.constraintlayout.widget.ConstraintLayout;
 import androidx.fragment.app.Fragment;
 import androidx.recyclerview.widget.RecyclerView;

app/src/main/java/fr/free/nrw/commons/upload/mediaDetails/UploadMediaDetailFragment.java

@@ -1,7 +1,6 @@
 package fr.free.nrw.commons.upload.mediaDetails;
 
 import static android.app.Activity.RESULT_OK;
-import static fr.free.nrw.commons.utils.ActivityUtils.startActivityWithFlags;
 
 import android.annotation.SuppressLint;
 import android.app.Activity;
@@ -45,6 +44,7 @@ import fr.free.nrw.commons.upload.UploadBaseFragment;
 import fr.free.nrw.commons.upload.UploadItem;
 import fr.free.nrw.commons.upload.UploadMediaDetail;
 import fr.free.nrw.commons.upload.UploadMediaDetailAdapter;
+import fr.free.nrw.commons.utils.ActivityUtils;
 import fr.free.nrw.commons.utils.DialogUtil;
 import fr.free.nrw.commons.utils.ImageUtils;
 import fr.free.nrw.commons.utils.NetworkUtils;
@@ -208,7 +208,7 @@ public class UploadMediaDetailFragment extends UploadBaseFragment implements
 
         try {
             if(!presenter.getImageQuality(indexOfFragment, inAppPictureLocation, getActivity())) {
-                startActivityWithFlags(
+                ActivityUtils.startActivityWithFlags(
                 getActivity(), MainActivity.class, Intent.FLAG_ACTIVITY_CLEAR_TOP,
                 Intent.FLAG_ACTIVITY_SINGLE_TOP);
             }

app/src/main/java/fr/free/nrw/commons/utils/AbstractTextWatcher.kt

@@ -1,31 +1,25 @@
-package fr.free.nrw.commons.utils;
+package fr.free.nrw.commons.utils
 
-import android.text.Editable;
-import android.text.TextWatcher;
+import android.text.Editable
+import android.text.TextWatcher
 
-import androidx.annotation.NonNull;
+class AbstractTextWatcher(
+    private val textChange: TextChange
+) : TextWatcher {
 
-public class AbstractTextWatcher implements TextWatcher {
-    private final TextChange textChange;
-
-    public AbstractTextWatcher(@NonNull TextChange textChange) {
-        this.textChange = textChange;
+    override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
+        // No-op
     }
 
-    @Override
-    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
+    override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
+        textChange.onTextChanged(s.toString())
     }
 
-    @Override
-    public void onTextChanged(CharSequence s, int start, int before, int count) {
-        textChange.onTextChanged(s.toString());
+    override fun afterTextChanged(s: Editable?) {
+        // No-op
     }
 
-    @Override
-    public void afterTextChanged(Editable s) {
-    }
-
-    public interface TextChange {
-        void onTextChanged(String value);
+    interface TextChange {
+        fun onTextChanged(value: String)
     }
 }

app/src/main/java/fr/free/nrw/commons/utils/ActivityUtils.kt

@@ -1,15 +1,16 @@
-package fr.free.nrw.commons.utils;
+package fr.free.nrw.commons.utils
 
-import android.content.Context;
-import android.content.Intent;
+import android.content.Context
+import android.content.Intent
 
-public class ActivityUtils {
+object ActivityUtils {
 
-    public static <T> void startActivityWithFlags(Context context, Class<T> cls, int... flags) {
-        Intent intent = new Intent(context, cls);
-        for (int flag : flags) {
-            intent.addFlags(flag);
+    @JvmStatic
+    fun <T> startActivityWithFlags(context: Context, cls: Class<T>, vararg flags: Int) {
+        val intent = Intent(context, cls)
+        for (flag in flags) {
+            intent.addFlags(flag)
         }
-        context.startActivity(intent);
+        context.startActivity(intent)
     }
-}
+}

app/src/main/java/fr/free/nrw/commons/utils/CommonsDateUtil.kt

@@ -1,44 +1,46 @@
-package fr.free.nrw.commons.utils;
+package fr.free.nrw.commons.utils
 
-import java.text.SimpleDateFormat;
-import java.util.Locale;
-import java.util.TimeZone;
+import java.text.SimpleDateFormat
+import java.util.Locale
+import java.util.TimeZone
 
 /**
- * Provides util functions for formatting date time
- * Most of our formatting needs are addressed by the data library's DateUtil class
- * Methods should be added here only if DateUtil class doesn't provide for it already
+ * Provides util functions for formatting date time.
+ * Most of our formatting needs are addressed by the data library's DateUtil class.
+ * Methods should be added here only if DateUtil class doesn't provide for it already.
  */
-public class CommonsDateUtil {
+object CommonsDateUtil {
 
     /**
-     * Gets SimpleDateFormat for short date pattern
+     * Gets SimpleDateFormat for short date pattern.
      * @return simpledateformat
      */
-    public static SimpleDateFormat getIso8601DateFormatShort() {
-        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.ROOT);
-        simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
-        return simpleDateFormat;
+    @JvmStatic
+    fun getIso8601DateFormatShort(): SimpleDateFormat {
+        val simpleDateFormat = SimpleDateFormat("yyyy-MM-dd", Locale.ROOT)
+        simpleDateFormat.timeZone = TimeZone.getTimeZone("UTC")
+        return simpleDateFormat
     }
 
     /**
-     * Gets SimpleDateFormat for date pattern returned by Media object
+     * Gets SimpleDateFormat for date pattern returned by Media object.
      * @return simpledateformat
      */
-    public static SimpleDateFormat getMediaSimpleDateFormat() {
-        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ROOT);
-        simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
-        return simpleDateFormat;
+    @JvmStatic
+    fun getMediaSimpleDateFormat(): SimpleDateFormat {
+        val simpleDateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ROOT)
+        simpleDateFormat.timeZone = TimeZone.getTimeZone("UTC")
+        return simpleDateFormat
     }
 
     /**
-     * Gets the timestamp pattern for a date
+     * Gets the timestamp pattern for a date.
      * @return timestamp
      */
-        public static SimpleDateFormat getIso8601DateFormatTimestamp() {
-            final SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'",
-                Locale.ROOT);
-            simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
-            return simpleDateFormat;
+    @JvmStatic
+    fun getIso8601DateFormatTimestamp(): SimpleDateFormat {
+        val simpleDateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ROOT)
+        simpleDateFormat.timeZone = TimeZone.getTimeZone("UTC")
+        return simpleDateFormat
     }
 }

app/src/main/java/fr/free/nrw/commons/utils/DateUtil.kt

@@ -1,53 +1,59 @@
-package fr.free.nrw.commons.utils;
+package fr.free.nrw.commons.utils
 
-import static android.text.format.DateFormat.getBestDateTimePattern;
+import android.text.format.DateFormat.getBestDateTimePattern
+import java.text.ParseException
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.HashMap
+import java.util.Locale
+import java.util.TimeZone
 
-import androidx.annotation.NonNull;
+/**
+ * Utility class for date formatting and parsing.
+ * TODO: Switch to DateTimeFormatter when minSdk = 26.
+ */
+object DateUtil {
 
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
-import java.util.Date;
-import java.util.HashMap;
-import java.util.Locale;
-import java.util.Map;
-import java.util.TimeZone;
+    private val DATE_FORMATS: MutableMap<String, SimpleDateFormat> = HashMap()
 
-public final class DateUtil {
-    private static Map<String, SimpleDateFormat> DATE_FORMATS = new HashMap<>();
-
-    // TODO: Switch to DateTimeFormatter when minSdk = 26.
-
-    public static synchronized String iso8601DateFormat(Date date) {
-        return getCachedDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ROOT, true).format(date);
+    @JvmStatic
+    @Synchronized
+    fun iso8601DateFormat(date: Date): String {
+        return getCachedDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ROOT, true).format(date)
     }
 
-    public static synchronized Date iso8601DateParse(String date) throws ParseException {
-        return getCachedDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ROOT, true).parse(date);
+    @JvmStatic
+    @Synchronized
+    @Throws(ParseException::class)
+    fun iso8601DateParse(date: String): Date {
+        return getCachedDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ROOT, true).parse(date)
     }
 
-    public static String getMonthOnlyDateString(@NonNull Date date) {
-        return getDateStringWithSkeletonPattern(date, "MMMM d");
+    @JvmStatic
+    fun getMonthOnlyDateString(date: Date): String {
+        return getDateStringWithSkeletonPattern(date, "MMMM d")
     }
 
-    public static String getExtraShortDateString(@NonNull Date date) {
-        return getDateStringWithSkeletonPattern(date, "MMM d");
+    @JvmStatic
+    fun getExtraShortDateString(date: Date): String {
+        return getDateStringWithSkeletonPattern(date, "MMM d")
     }
 
-    public static synchronized String getDateStringWithSkeletonPattern(@NonNull Date date, @NonNull String pattern) {
-        return getCachedDateFormat(getBestDateTimePattern(Locale.getDefault(), pattern), Locale.getDefault(), false).format(date);
+    @JvmStatic
+    @Synchronized
+    fun getDateStringWithSkeletonPattern(date: Date, pattern: String): String {
+        return getCachedDateFormat(getBestDateTimePattern(Locale.getDefault(), pattern), Locale.getDefault(), false).format(date)
     }
 
-    private static SimpleDateFormat getCachedDateFormat(String pattern, Locale locale, boolean utc) {
+    @JvmStatic
+    private fun getCachedDateFormat(pattern: String, locale: Locale, utc: Boolean): SimpleDateFormat {
         if (!DATE_FORMATS.containsKey(pattern)) {
-            SimpleDateFormat df = new SimpleDateFormat(pattern, locale);
+            val df = SimpleDateFormat(pattern, locale)
             if (utc) {
-                df.setTimeZone(TimeZone.getTimeZone("UTC"));
+                df.timeZone = TimeZone.getTimeZone("UTC")
             }
-            DATE_FORMATS.put(pattern, df);
+            DATE_FORMATS[pattern] = df
         }
-        return DATE_FORMATS.get(pattern);
-    }
-
-    private DateUtil() {
+        return DATE_FORMATS[pattern]!!
     }
 }

app/src/main/java/fr/free/nrw/commons/wikidata/model/notifications/Notification.java

@@ -7,8 +7,8 @@ import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.annotations.SerializedName;
 
-import org.apache.commons.lang3.StringUtils;
 import fr.free.nrw.commons.utils.DateUtil;
+import org.apache.commons.lang3.StringUtils;
 import fr.free.nrw.commons.wikidata.GsonUtil;
 
 import java.text.ParseException;