Self explanatory O(n) easy to understand using Java
\nclass OrderedStream {\n    private String[] streams;\n    private int counter = 0;\n    public OrderedStream(int n) {\n        streams = new String[n];\n    }
```\nclass OrderedStream {\n    private String[] streams;\n    private int counter = 0;\n    public OrderedStream(int n) {\n        streams = new String[n];\n    }\n    \n    public List<String> insert(int idKey, String value) {\n        List<String> stream = new ArrayList<String>();\n        streams[idKey-1] = value;\n        while (counter < streams.length && streams[counter] != null) \n        {\n\t\tstream.add(streams[counter]);\n\t\tcounter++;\n\t    }\n        return stream;\n    }\n}\n```\n\nPS: Do upvote if you like the solution and understood it easily :-)
['Array', 'Java']