Instructions

Test suite

Solution

There are 10 types of people in the world: Those who understand binary, and those who don't.

You and your fellow cohort of those in the "know" when it comes to binary decide to come up with a secret "handshake".

1 = wink
10 = double blink
100 = close your eyes
1000 = jump


10000 = Reverse the order of the operations in the secret handshake.

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

Here's a couple of examples:

Given the input 3, the function would return the array ["wink", "double blink"] because 3 is 11 in binary.

Given the input 19, the function would return the array ["double blink", "wink"] because 19 is 10011 in binary. Notice that the addition of 16 (10000 in binary) has caused the array to be reversed.

Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

$ gradle test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore("Remove to run test") annotation.

Source

Bert, in Mary Poppins http://www.imdb.com/title/tt0058331/quotes/qt0437047

Submitting Incomplete Solutions

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

HandshakeCalculatorTest.java

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

import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static java.util.Collections.singletonList;
import static org.junit.Assert.assertEquals;

public class HandshakeCalculatorTest {

    private HandshakeCalculator handshakeCalculator;

    @Before
    public void setUp() {
        handshakeCalculator = new HandshakeCalculator();
    }

    @Test
    public void testThatInput1YieldsAWink() {
        assertEquals(
                singletonList(Signal.WINK),
                handshakeCalculator.calculateHandshake(1));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatInput2YieldsADoubleBlink() {
        assertEquals(
                singletonList(Signal.DOUBLE_BLINK),
                handshakeCalculator.calculateHandshake(2));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatInput4YieldsACloseYourEyes() {
        assertEquals(
                singletonList(Signal.CLOSE_YOUR_EYES),
                handshakeCalculator.calculateHandshake(4));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatInput8YieldsAJump() {
        assertEquals(
                singletonList(Signal.JUMP),
               handshakeCalculator.calculateHandshake(8));
    }

    @Ignore("Remove to run test")
    @Test
    public void testAnInputThatYieldsTwoActions() {
        assertEquals(
                asList(Signal.WINK, Signal.DOUBLE_BLINK),
                handshakeCalculator.calculateHandshake(3));
    }

    @Ignore("Remove to run test")
    @Test
    public void testAnInputThatYieldsTwoReversedActions() {
        assertEquals(
                asList(Signal.DOUBLE_BLINK, Signal.WINK),
               handshakeCalculator.calculateHandshake(19));
    }

    @Ignore("Remove to run test")
    @Test
    public void testReversingASingleActionYieldsTheSameAction() {
        assertEquals(
                singletonList(Signal.JUMP),
                handshakeCalculator.calculateHandshake(24));
    }

    @Ignore("Remove to run test")
    @Test
    public void testReversingNoActionsYieldsNoActions() {
        assertEquals(
                emptyList(),
                handshakeCalculator.calculateHandshake(16));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputThatYieldsAllActions() {
        assertEquals(
                asList(Signal.WINK, Signal.DOUBLE_BLINK, Signal.CLOSE_YOUR_EYES, Signal.JUMP),
                handshakeCalculator.calculateHandshake(15));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputThatYieldsAllActionsReversed() {
        assertEquals(
                asList(Signal.JUMP, Signal.CLOSE_YOUR_EYES, Signal.DOUBLE_BLINK, Signal.WINK),
                handshakeCalculator.calculateHandshake(31));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatInput0YieldsNoActions() {
        assertEquals(
                emptyList(),
                handshakeCalculator.calculateHandshake(0));
    }

}

src/main/java/HandshakeCalculator.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class HandshakeCalculator {

    private final Map<Integer, Signal> mapping = new HashMap<>();

    public HandshakeCalculator() {
        mapping.put(1, Signal.WINK);
        mapping.put(2, Signal.DOUBLE_BLINK);
        mapping.put(4, Signal.CLOSE_YOUR_EYES);
        mapping.put(8, Signal.JUMP);
    }

    List<Signal> calculateHandshake(int number) {
        List<Signal> signals = new ArrayList<>();

        mapping.forEach((key, value) -> {
            if ((number & key) == key) {
                signals.add(value);
            }
        });

        if ((number & 16) == 16) {
            Collections.reverse(signals);
        }

        return signals;
    }

}

src/main/java/Signal.java

enum Signal {

    WINK, DOUBLE_BLINK, CLOSE_YOUR_EYES, JUMP

}

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