Trying to fix #460

Actually, could not reproduce this, added some tests (they passed on initial version).

classlib/src/main/java/org/teavm/classlib/impl/ServiceLoaderSupport.java

@@ -61,12 +61,13 @@ public class ServiceLoaderSupport extends AbstractDependencyListener implements
         for (Map.Entry<String, List<String>> entry : serviceMap.entrySet()) {
             writer.appendClass(entry.getKey()).append(".$$serviceList$$ = [");
             List<String> implementations = entry.getValue();
-            for (int i = 0; i < implementations.size(); ++i) {
+            boolean first = true;
-                if (i > 0) {
+            for (String implName : implementations) {
-                    writer.append(", ");
-                }
-                String implName = implementations.get(i);
                 if (context.getClassSource().getClassNames().contains(implName)) {
+                    if (!first) {
+                        writer.append(", ");
+                    }
+                    first = false;
                     writer.append("[").appendClass(implName).append(", ").appendMethodBody(
                             new MethodReference(implName, INIT_METHOD))
                             .append("]");

tests/src/test/java/org/teavm/classlib/java/util/MultipleTestService.java

@@ -0,0 +1,20 @@
+/*
+ *  Copyright 2020 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.util;
+
+public interface MultipleTestService {
+    String foo();
+}

tests/src/test/java/org/teavm/classlib/java/util/MultipleTestServiceImpl1.java

@@ -0,0 +1,23 @@
+/*
+ *  Copyright 2020 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.util;
+
+public class MultipleTestServiceImpl1 implements MultipleTestService {
+    @Override
+    public String foo() {
+        return "A";
+    }
+}

tests/src/test/java/org/teavm/classlib/java/util/MultipleTestServiceImpl2.java

@@ -0,0 +1,23 @@
+/*
+ *  Copyright 2020 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.util;
+
+public class MultipleTestServiceImpl2 implements MultipleTestService {
+    @Override
+    public String foo() {
+        return "B";
+    }
+}

tests/src/test/java/org/teavm/classlib/java/util/ServiceLoaderTest.java

@@ -16,6 +16,9 @@
 package org.teavm.classlib.java.util;
 
 import static org.junit.Assert.assertEquals;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 import java.util.ServiceLoader;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -30,4 +33,14 @@ public class ServiceLoaderTest {
         assertEquals(TestServiceImpl.class, instance.getClass());
         assertEquals(1, ((TestServiceImpl) instance).getCounter());
     }
+
+    @Test
+    public void loadsMultipleServices() {
+        List<String> strings = new ArrayList<>();
+        for (MultipleTestService instance : ServiceLoader.load(MultipleTestService.class)) {
+            strings.add(instance.foo());
+        }
+        strings.sort(String::compareTo);
+        assertEquals(Arrays.asList("A", "B"), strings);
+    }
 }

tests/src/test/resources/META-INF/services/org.teavm.classlib.java.util.MultipleTestService

@@ -0,0 +1,18 @@
+#
+#  Copyright 2017 Alexey Andreev.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+org.teavm.classlib.java.util.MultipleTestServiceImpl1
+org.teavm.classlib.java.util.MultipleTestServiceImpl2