Digit kata (format numbers for digital display). Java 7 Dependencies: Guava 13.0.1, junit 4.11, fest-assert-core 2.0M8

Digits.java

package test.kata_digit;

import java.util.ArrayList;
import java.util.List;

import com.google.common.base.Joiner;

public class Digits {

    private static final int HEIGHT = 5;
    private static final Joiner LINE_JOINER = Joiner.on("\n");
    private static final Joiner COL_JOINER = Joiner.on(" ");

    private static final String[] ZERO = {
            " - ",
            "| |",
            "| |",
            "| |",
            " - "
    };

    private static final String[] ONE = {
            "  |",
            "  |",
            "  |",
            "  |",
            "  |"
    };

    private static final String[] TWO = {
            "-- ",
            "  |",
            " - ",
            "|  ",
            " --"
    };

    private static final String[] THREE = {
            "-- ",
            "  |",
            " -|",
            "  |",
            "-- "
    };

    private static final String[] FOUR = {
            "| |",
            "| |",
            " -|",
            "  |",
            "  |"
    };

    private static final String[] FIVE = {
            " --",
            "|  ",
            " - ",
            "  |",
            "-- "
    };

    private static final String[] SIX = {
            "|  ",
            "|  ",
            "|- ",
            "| |",
            " - "
    };

    private static final String[] SEVEN = {
            "---",
            "  |",
            "  |",
            "  |",
            "  |"
    };

    private static final String[] EIGHT = {
            " - ",
            "| |",
            "|-|",
            "| |",
            " - "
    };

    private static final String[] NINE = {
            " - ",
            "| |",
            " -|",
            "  |",
            " - "
    };

    private static final String[][] DIGITS = {
            ZERO, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE
    };

    public static String toDigit(int value) {
        String stringValue = String.valueOf(value);
        List<String> result = new ArrayList<>();

        for (int row = 0; row < HEIGHT; row++) {
            List<String> digitRow = new ArrayList<>();

            for (byte c : stringValue.getBytes()) {
                int digit = c - '0';
                digitRow.add(DIGITS[digit][row]);
            }

            result.add(COL_JOINER.join(digitRow));
        }

        return LINE_JOINER.join(result);
    }
}

DigitTest.java

package test.kata_digit;

import static org.fest.assertions.api.Assertions.assertThat;

import org.junit.Test;

public class DigitTest {

    @Test
    public void should_get_digital_one_when_1() throws Exception {
        String digits = Digits.toDigit(1);

        assertThat(digits).isEqualTo(
                "  |\n" +
                "  |\n" +
                "  |\n" +
                "  |\n" +
                "  |"
        );
    }

    @Test
    public void should_get_digital_one_two_when_12() throws Exception {
        String digits = Digits.toDigit(12);

        assertThat(digits).isEqualTo(
                "  | -- \n" +
                "  |   |\n" +
                "  |  - \n" +
                "  | |  \n" +
                "  |  --"
        );
    }

    @Test
    public void should_get_digital_five_one_two_when_512() throws Exception {
        String digits = Digits.toDigit(512);

        assertThat(digits).isEqualTo(
                " --   | -- \n" +
                "|     |   |\n" +
                " -    |  - \n" +
                "  |   | |  \n" +
                "--    |  --"
        );
    }

}