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rootulp's solution

to Space Age in the Java Track

Published at Jul 13 2018 · 0 comments
Test suite


This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Given an age in seconds, calculate how old someone would be on:

  • Earth: orbital period 365.25 Earth days, or 31557600 seconds
  • Mercury: orbital period 0.2408467 Earth years
  • Venus: orbital period 0.61519726 Earth years
  • Mars: orbital period 1.8808158 Earth years
  • Jupiter: orbital period 11.862615 Earth years
  • Saturn: orbital period 29.447498 Earth years
  • Uranus: orbital period 84.016846 Earth years
  • Neptune: orbital period 164.79132 Earth years

So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.

If you're wondering why Pluto didn't make the cut, go watch this youtube video.

Running the tests

You can run all the tests for an exercise by entering

$ gradle test

in your terminal.


Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01

Submitting Incomplete Solutions

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


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

import static org.junit.Assert.assertEquals;

public class SpaceAgeTest {

    private static final double MAXIMUM_DELTA = 1E-02;

    public void ageOnEarth() {
        SpaceAge age = new SpaceAge(1000000000);

        assertEquals(31.69, age.onEarth(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnMercury() {
        SpaceAge age = new SpaceAge(2134835688);

        assertEquals(280.88, age.onMercury(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnVenus() {
        SpaceAge age = new SpaceAge(189839836);

        assertEquals(9.78, age.onVenus(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnMars() {
        SpaceAge age = new SpaceAge(2329871239L);

        assertEquals(39.25, age.onMars(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnJupiter() {
        SpaceAge age = new SpaceAge(901876382);

        assertEquals(2.41, age.onJupiter(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnSaturn() {
        SpaceAge age = new SpaceAge(3000000000L);

        assertEquals(3.23, age.onSaturn(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnUranus() {
        SpaceAge age = new SpaceAge(3210123456L);

        assertEquals(1.21, age.onUranus(), MAXIMUM_DELTA);

    @Ignore("Remove to run test")
    public void ageOnNeptune() {
        SpaceAge age = new SpaceAge(8210123456L);

        assertEquals(1.58, age.onNeptune(), MAXIMUM_DELTA);
public class SpaceAge {

  private final double seconds;
  private static final double MAXIMUM_DELTA = 1E-02;
  private enum Planet {
    EARTH   (31557600),
    MERCURY (0.2408467),
    VENUS   (0.61519726),
    MARS    (1.8808158),
    JUPITER (11.862615),
    SATURN  (29.447498),
    URANUS  (84.016846),
    NEPTUNE (164.79132);

    // op -> Orbital Period relative to Earth years
    private final double op;
    Planet (double op) { this.op = op; }
    private final double op() { return this.op; }


  public SpaceAge(double seconds) {
    this.seconds = seconds;

  public double getSeconds() {
    return this.seconds;

  public double onEarth() {
    return getSeconds() / Planet.EARTH.op();

  public double onMercury() {
    return onEarth() / Planet.MERCURY.op();

  public double onVenus() {
    return onEarth() / Planet.VENUS.op();

  public double onMars() {
    return onEarth() / Planet.MARS.op();

  public double onJupiter() {
    return onEarth() / Planet.JUPITER.op();

  public double onSaturn() {
    return onEarth() / Planet.SATURN.op();

  public double onUranus() {
    return onEarth() / Planet.URANUS.op();

  public double onNeptune() {
    return onEarth() / Planet.NEPTUNE.op();

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