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TextIO Read
-----------

When you create a pipeline, you often need to read data from some external source, such as a file
or a database. Likewise, you may want your pipeline to output its result data to an external
storage system. Beam provides read and write transforms for a number of common data storage types.
If you want your pipeline to read from or write to a data storage format that isn’t supported by
the built-in transforms, you can implement your own read and write transforms.

To read a PCollection from one or more text files, use TextIO.read() to instantiate a transform
and use TextIO.Read.from(String) to specify the path of the file(s) to be read.

**Kata:** Read the 'countries.txt' file and convert each country name into uppercase.

<div class="hint">
  Use <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/TextIO.html">
  TextIO</a> and its corresponding
  <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/io/TextIO.html#read--">
    TextIO.read()</a> method.
</div>

<div class="hint">
  Refer to the Beam Programming Guide
  <a href="https://beam.apache.org/documentation/programming-guide/#pipeline-io-reading-data">
    "Reading input data"</a> section for more information.
</div>