/guava/guava/src/com/google/common/io/Files.java
if ( files != null) {   return unmodifiableList( asList( files) ) ; }
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return Traverser.forTree(FILE_TREE); } private static final SuccessorsFunction<File> FILE_TREE = new SuccessorsFunction<File>() { @Override public Iterable<File> successors(File file) { <extra_id_0> File[] files = file.listFiles(); if (files != null) { return Collections.unmodifiableList(Arrays.asList(files)); } } return ImmutableList.of();