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JaeHyoLee's solution

to ETL in the Java Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

We are going to do the Transform step of an Extract-Transform-Load.

ETL

Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so we're going to migrate this."

(Typically, this is followed by, "We're only going to need to run this once." That's then typically followed by much forehead slapping and moaning about how stupid we could possibly be.)

The goal

We're going to extract some scrabble scores from a legacy system.

The old system stored a list of letters per score:

  • 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
  • 2 points: "D", "G",
  • 3 points: "B", "C", "M", "P",
  • 4 points: "F", "H", "V", "W", "Y",
  • 5 points: "K",
  • 8 points: "J", "X",
  • 10 points: "Q", "Z",

The shiny new scrabble system instead stores the score per letter, which makes it much faster and easier to calculate the score for a word. It also stores the letters in lower-case regardless of the case of the input letters:

  • "a" is worth 1 point.
  • "b" is worth 3 points.
  • "c" is worth 3 points.
  • "d" is worth 2 points.
  • Etc.

Your mission, should you choose to accept it, is to transform the legacy data format to the shiny new format.

Notes

A final note about scoring, Scrabble is played around the world in a variety of languages, each with its own unique scoring table. For example, an "E" is scored at 2 in the Māori-language version of the game while being scored at 4 in the Hawaiian-language version.

Running the tests

You can run all the tests for an exercise by entering

$ gradle test

in your terminal.

Source

The Jumpstart Lab team http://jumpstartlab.com

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

EtlTest.java

import org.junit.Test;
import org.junit.Ignore;

import java.util.*;

import static org.junit.Assert.assertEquals;


public class EtlTest {
    private final Etl etl = new Etl();

    @Test
    public void testTransformOneValue() {
        Map<Integer, List<String>> old = new HashMap<Integer, List<String>>() {
            {
                put(1, Arrays.asList("A"));
            }
        };
        old = Collections.unmodifiableMap(old);

        Map<String, Integer> expected = new HashMap<String, Integer>() {
            {
                put("a", 1);
            }
        };
        expected = Collections.unmodifiableMap(expected);

        assertEquals(expected, etl.transform(old));
    }

    @Ignore("Remove to run test")
    @Test
    public void testTransformMoreValues() {
        Map<Integer, List<String>> old = new HashMap<Integer, List<String>>() {
            {
                put(1, Arrays.asList("A", "E", "I", "O", "U"));
            }
        };
        old = Collections.unmodifiableMap(old);

        Map<String, Integer> expected = new HashMap<String, Integer>() {
            {
                put("a", 1);
                put("e", 1);
                put("i", 1);
                put("o", 1);
                put("u", 1);
            }
        };
        expected = Collections.unmodifiableMap(expected);

        assertEquals(expected, etl.transform(old));
    }

    @Ignore("Remove to run test")
    @Test
    public void testMoreKeys() {
        Map<Integer, List<String>> old = new HashMap<Integer, List<String>>() {
            {
                put(1, Arrays.asList("A", "E"));
                put(2, Arrays.asList("D", "G"));
            }
        };
        old = Collections.unmodifiableMap(old);

        Map<String, Integer> expected = new HashMap<String, Integer>() {
            {
                put("a", 1);
                put("e", 1);
                put("d", 2);
                put("g", 2);
            }
        };
        expected = Collections.unmodifiableMap(expected);

        assertEquals(expected, etl.transform(old));
    }

    @Ignore("Remove to run test")
    @Test
    public void testFullDataset() {
        Map<Integer, List<String>> old = new HashMap<Integer, List<String>>() {
            {
                put(1, Arrays.asList("A", "E", "I", "O", "U", "L", "N", "R", "S", "T"));
                put(2, Arrays.asList("D", "G"));
                put(3, Arrays.asList("B", "C", "M", "P"));
                put(4, Arrays.asList("F", "H", "V", "W", "Y"));
                put(5, Arrays.asList("K"));
                put(8, Arrays.asList("J", "X"));
                put(10, Arrays.asList("Q", "Z"));
            }
        };
        old = Collections.unmodifiableMap(old);

        Map<String, Integer> expected = new HashMap<String, Integer>() {
            {
                put("a", 1);
                put("b", 3);
                put("c", 3);
                put("d", 2);
                put("e", 1);
                put("f", 4);
                put("g", 2);
                put("h", 4);
                put("i", 1);
                put("j", 8);
                put("k", 5);
                put("l", 1);
                put("m", 3);
                put("n", 1);
                put("o", 1);
                put("p", 3);
                put("q", 10);
                put("r", 1);
                put("s", 1);
                put("t", 1);
                put("u", 1);
                put("v", 4);
                put("w", 4);
                put("x", 8);
                put("y", 4);
                put("z", 10);
            }
        };
        expected = Collections.unmodifiableMap(expected);

        assertEquals(expected, etl.transform(old));
    }
}
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Etl {

	public Map<String, Integer> transform(Map<Integer, List<String>> old) {
		Map<String, Integer> transformedMap = new HashMap<String, Integer>();

		for (int key : old.keySet()) {
			List l = old.get(key);
			Iterator<String> it = l.iterator();
			while (it.hasNext()) {
				String s = it.next();
				transformedMap.put(s.toLowerCase(), key);
			}
		}
		return transformedMap;
	}
}

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