How to update value of specific embedded document, inside an array, of a specific document in MongoDB?

Here is RameshVel's solution translated to java:

    DB db = conn.getDB( "yourDB" ); 
    DBCollection coll = db.getCollection( "yourCollection" );

    ObjectId _id = new ObjectId("4e71b07ff391f2b283be2f95");
    ObjectId arrayId = new ObjectId("4e639a918dca838d4575979c");

    BasicDBObject query = new BasicDBObject();
    query.put("_id", _id);
    query.put("array._arrayId", arrayId);

    BasicDBObject data = new BasicDBObject();
    data.put("array.$.someField", "updated");

    BasicDBObject command = new BasicDBObject();
    command.put("$set", data);

    coll.update(query, command);

You could still use $ positional operator to accomplish this. But you need to specify the objectid of the parent doc along with the _arrayid filter. The below command line query works fine

db.so.update({_id:ObjectId("4e719eb07f1d878c5cf7333c"),
              "array._arrayId":ObjectId("dsd87dsa9d87s9d7")},
              {$set:{"array.$.someField":"updated"}})