revert integration of PR #1071 which wasn't ready

Author: stephengold

jme3-core/src/main/java/com/jme3/anim/AnimComposer.java

@@ -3,10 +3,7 @@
 import com.jme3.anim.tween.Tween;
 import com.jme3.anim.tween.Tweens;
 import com.jme3.anim.tween.action.*;
-import com.jme3.export.InputCapsule;
-import com.jme3.export.JmeExporter;
-import com.jme3.export.JmeImporter;
-import com.jme3.export.OutputCapsule;
+import com.jme3.export.*;
 import com.jme3.renderer.RenderManager;
 import com.jme3.renderer.ViewPort;
 import com.jme3.scene.control.AbstractControl;
@@ -209,25 +206,12 @@ public void reset() {
         }
     }
 
-    /**
-     * Returns an unmodifiable set of all available animations. When an attempt
-     * is made to modify the set, an UnsupportedOperationException is thrown.
-     *
-     * @return the unmodifiable set of animations
-     */
-    public Set<AnimClip> getAnimClips() {
-        return Collections.unmodifiableSet(new HashSet<>(animClipMap.values()));
+    public Collection<AnimClip> getAnimClips() {
+        return Collections.unmodifiableCollection(animClipMap.values());
     }
 
-    /**
-     * Returns an unmodifiable set of all available animation names. When an
-     * attempt is made to modify the set, an UnsupportedOperationException is
-     * thrown.
-     *
-     * @return the unmodifiable set of animation names.
-     */
-    public Set<String> getAnimClipsNames() {
-        return Collections.unmodifiableSet(animClipMap.keySet());
+    public Collection<String> getAnimClipsNames() {
+        return Collections.unmodifiableCollection(animClipMap.keySet());
     }
 
     @Override