Use String.join() and Collectors.joining().

extractor/src/main/java/org/schabi/newpipe/extractor/services/bandcamp/extractors/BandcampStreamExtractor.java

@@ -136,13 +136,8 @@ public class BandcampStreamExtractor extends StreamExtractor {
     @Nonnull
     @Override
     public Description getDescription() {
-        final String s = Utils.nonEmptyAndNullJoin(
-                "\n\n",
-                new String[] {
-                        current.getString("about"),
-                        current.getString("lyrics"),
-                        current.getString("credits")
-                });
+        final String s = Utils.nonEmptyAndNullJoin("\n\n", current.getString("about"),
+                current.getString("lyrics"), current.getString("credits"));
         return new Description(s, Description.PLAIN_TEXT);
     }
 

extractor/src/main/java/org/schabi/newpipe/extractor/services/soundcloud/extractors/SoundcloudPlaylistExtractor.java

@@ -16,7 +16,6 @@ import org.schabi.newpipe.extractor.playlist.PlaylistExtractor;
 import org.schabi.newpipe.extractor.services.soundcloud.SoundcloudParsingHelper;
 import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 import org.schabi.newpipe.extractor.stream.StreamInfoItemsCollector;
-import org.schabi.newpipe.extractor.utils.Utils;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -165,7 +164,7 @@ public class SoundcloudPlaylistExtractor extends PlaylistExtractor {
         }
 
         final String currentPageUrl = SOUNDCLOUD_API_V2_URL + "tracks?client_id="
-                + SoundcloudParsingHelper.clientId() + "&ids=" + Utils.join(",", currentIds);
+                + SoundcloudParsingHelper.clientId() + "&ids=" + String.join(",", currentIds);
 
         final StreamInfoItemsCollector collector = new StreamInfoItemsCollector(getServiceId());
         final String response = NewPipe.getDownloader().get(currentPageUrl,

extractor/src/main/java/org/schabi/newpipe/extractor/utils/Utils.java

@@ -6,15 +6,12 @@ import java.io.UnsupportedEncodingException;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLDecoder;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Iterator;
-import java.util.LinkedList;
-import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -310,31 +307,14 @@ public final class Utils {
         return true;
     }
 
-    @Nonnull
-    public static String join(final CharSequence delimiter,
-                              @Nonnull final Iterable<? extends CharSequence> elements) {
-        final StringBuilder stringBuilder = new StringBuilder();
-        final Iterator<? extends CharSequence> iterator = elements.iterator();
-        while (iterator.hasNext()) {
-            stringBuilder.append(iterator.next());
-            if (iterator.hasNext()) {
-                stringBuilder.append(delimiter);
-            }
-        }
-        return stringBuilder.toString();
-    }
-
     @Nonnull
     public static String join(
             final String delimiter,
             final String mapJoin,
             @Nonnull final Map<? extends CharSequence, ? extends CharSequence> elements) {
-        final List<String> list = new LinkedList<>();
-        for (final Map.Entry<? extends CharSequence, ? extends CharSequence> entry
-                : elements.entrySet()) {
-            list.add(entry.getKey() + mapJoin + entry.getValue());
-        }
-        return join(delimiter, list);
+        return elements.entrySet().stream()
+                .map(entry -> entry.getKey() + mapJoin + entry.getValue())
+                .collect(Collectors.joining(delimiter));
     }
 
     /**
@@ -342,10 +322,10 @@ public final class Utils {
      */
     @Nonnull
     public static String nonEmptyAndNullJoin(final CharSequence delimiter,
-                                             final String[] elements) {
-        final List<String> list = new ArrayList<>(Arrays.asList(elements));
-        list.removeIf(s -> isNullOrEmpty(s) || s.equals("null"));
-        return join(delimiter, list);
+                                             final String... elements) {
+        return Arrays.stream(elements)
+                .filter(s -> !isNullOrEmpty(s) && !s.equals("null"))
+                .collect(Collectors.joining(delimiter));
     }
 
     /**

extractor/src/test/java/org/schabi/newpipe/extractor/utils/UtilsTest.java

@@ -3,9 +3,6 @@ package org.schabi.newpipe.extractor.utils;
 import org.junit.jupiter.api.Test;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 
-import javax.annotation.Nonnull;
-import java.util.Arrays;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 class UtilsTest {
@@ -20,8 +17,8 @@ class UtilsTest {
 
     @Test
     void testJoin() {
-        assertEquals("some,random,stuff", Utils.join(",", Arrays.asList("some", "random", "stuff")));
-        assertEquals("some,random,not-null,stuff", Utils.nonEmptyAndNullJoin(",", new String[]{"some", "null", "random", "", "not-null", null, "stuff"}));
+        assertEquals("some,random,not-null,stuff", Utils.nonEmptyAndNullJoin(",",
+                "some", "null", "random", "", "not-null", null, "stuff"));
     }
 
     @Test