Greeter.java

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package pascal.orz.cn.sandbox.problem02;

import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

/**
 *
 * @author koduki
 */
public class Greeter {

    public Greeter() {
    }

    public String greet(int hour, int minute, Locale locale) {
        Time time = getTime(hour, minute);
        String message = getMessage(time, locale);

        return message;
    }

    public String greet(Date time, Locale locale) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(time);

        return this.greet(cal.get(Calendar.HOUR_OF_DAY), cal.get(Calendar.MINUTE), locale);
    }

    String getMessage(Time time, Locale locale) {
        String message;
        if (Locale.JAPAN == locale) {
            message = getMessageJP(time);
        } else if (Locale.ENGLISH == locale) {
            message = getMessageEN(time);
        } else {
            message = null;
        }
        return message;
    }

    String getMessageJP(Time time) {
        String message;
        switch (time) {
            case MORNING:
                message = "おはようございます";
                break;
            case AFTERNOON:
                message = "こんにちは";
                break;
            case EVENING:
                message = "こんばんは";
                break;
            default:
                message = null;
        }
        return message;
    }

    String getMessageEN(Time time) {
        String message;
        switch (time) {
            case MORNING:
                message = "Good Morning";
                break;
            case AFTERNOON:
                message = "Good Afternoon";
                break;
            case EVENING:
                message = "Good Evening";
                break;
            default:
                message = null;
        }
        return message;
    }

    Time getTime(int hour, int minute) throws IllegalArgumentException {
        if (!(0 <= minute && minute <= 59)) {
            throw new IllegalArgumentException("argument is from 00:00, to 23:59.");
        }

        if (5 <= hour && hour < 12) {
            return Time.MORNING;
        } else if (12 <= hour && hour < 18) {
            return Time.AFTERNOON;
        } else if (((18 <= hour && hour <= 23)) || (hour < 5)) {
            return Time.EVENING;
        } else {
            throw new IllegalArgumentException("argument is from 00:00, to 23:59.");
        }
    }
}

GreeterTest.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
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package pascal.orz.cn.sandbox.problem02;

import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import org.junit.Test;
import static org.junit.Assert.*;
import static org.hamcrest.core.Is.*;

/**
 *
 * @author koduki
 */
public class GreeterTest {

    public GreeterTest() {
    }

    public Date time(int h, int m) {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.HOUR_OF_DAY, h);
        cal.set(Calendar.MINUTE, m);
        cal.setLenient(false);

        return cal.getTime();
    }

    @Test
    public void getTimeWithMorning() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getTime(5, 0), is(Time.MORNING));
        assertThat(greeter.getTime(11, 59), is(Time.MORNING));
    }

    @Test
    public void getTimeWithAfternoon() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getTime(12, 0), is(Time.AFTERNOON));
        assertThat(greeter.getTime(17, 59), is(Time.AFTERNOON));
    }

    @Test
    public void ggetTimeWithEvening() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getTime(18, 0), is(Time.EVENING));
        assertThat(greeter.getTime(23, 0), is(Time.EVENING));
        assertThat(greeter.getTime(4, 59), is(Time.EVENING));
    }

    @Test(expected = IllegalArgumentException.class)
    public void getTimeWithIvalidHour() {
        Greeter greeter = new Greeter();
        greeter.getTime(24, 0);
    }

    @Test(expected = IllegalArgumentException.class)
    public void getTimeWithIvalidMinute() {
        Greeter greeter = new Greeter();
        greeter.getTime(23, 60);
    }

    @Test
    public void getMessageWithMorningAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.MORNING, Locale.JAPAN), is("おはようございます"));
    }

    @Test
    public void getMessageWithAfternoonAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.AFTERNOON, Locale.JAPAN), is("こんにちは"));
    }

    @Test
    public void getMessageWithEveningAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.EVENING, Locale.JAPAN), is("こんばんは"));
    }

    @Test
    public void getMessageWithMorningAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.MORNING, Locale.ENGLISH), is("Good Morning"));
    }

    @Test
    public void getMessageWithAfternoonAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.AFTERNOON, Locale.ENGLISH), is("Good Afternoon"));
    }

    @Test
    public void getMessageWithEveningAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.EVENING, Locale.ENGLISH), is("Good Evening"));
    }

    @Test
    public void greeterWithAndJa() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(6, 0), Locale.JAPAN), is("おはようございます"));
        assertThat(greeter.greet(time(12, 0), Locale.JAPAN), is("こんにちは"));
        assertThat(greeter.greet(time(23, 0), Locale.JAPAN), is("こんばんは"));
    }

    @Test
    public void greeterWithAndEn() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(6, 0), Locale.ENGLISH), is("Good Morning"));
        assertThat(greeter.greet(time(12, 0), Locale.ENGLISH), is("Good Afternoon"));
        assertThat(greeter.greet(time(23, 0), Locale.ENGLISH), is("Good Evening"));
    }
}

GreeterTest2.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package pascal.orz.cn.sandbox.problem02;

import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import lombok.AllArgsConstructor;
import lombok.ToString;
import org.junit.Test;
import static org.junit.Assert.*;
import static org.hamcrest.core.Is.*;
import org.junit.experimental.theories.DataPoints;
import org.junit.experimental.theories.Theories;
import org.junit.experimental.theories.Theory;
import org.junit.runner.RunWith;

/**
 *
 * @author koduki
 */
@RunWith(Theories.class)
public class GreeterTest2 {

    public GreeterTest2() {
    }

    public Date time(int h, int m) {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.HOUR_OF_DAY, h);
        cal.set(Calendar.MINUTE, m);
        cal.setLenient(false);

        return cal.getTime();
    }

    @ToString
    @AllArgsConstructor
    public static class GetTimeParameter {

        int hour;
        int minute;
        Time expected;
    }

    @DataPoints
    public static GetTimeParameter[] moning() {
        GetTimeParameter[] dataset = {
            new GetTimeParameter(5, 0, Time.MORNING),
            new GetTimeParameter(11, 59, Time.MORNING)
        };
        return dataset;
    }

    @DataPoints
    public static GetTimeParameter[] afternoon() {
        GetTimeParameter[] dataset = {
            new GetTimeParameter(12, 0, Time.AFTERNOON),
            new GetTimeParameter(17, 59, Time.AFTERNOON)
        };
        return dataset;
    }

    @DataPoints
    public static GetTimeParameter[] evening() {
        GetTimeParameter[] dataset = {
            new GetTimeParameter(18, 0, Time.EVENING),
            new GetTimeParameter(23, 59, Time.EVENING),
            new GetTimeParameter(4, 59, Time.EVENING)
        };
        return dataset;
    }

    @Theory
    public void getTimeWith(GetTimeParameter parameter) {
        Greeter greeter = new Greeter();
        assertThat(parameter.toString(), greeter.getTime(parameter.hour, parameter.minute), is(parameter.expected));
    }

    @Test(expected = IllegalArgumentException.class)
    public void getTimeWithIvalidHour() {
        Greeter greeter = new Greeter();
        greeter.getTime(24, 0);
    }

    @Test(expected = IllegalArgumentException.class)
    public void getTimeWithIvalidMinute() {
        Greeter greeter = new Greeter();
        greeter.getTime(23, 60);
    }

    @Test
    public void getMessageWithMorningAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.MORNING, Locale.JAPAN), is("おはようございます"));
    }

    @Test
    public void getMessageWithAfternoonAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.AFTERNOON, Locale.JAPAN), is("こんにちは"));
    }

    @Test
    public void getMessageWithEveningAndJA() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.EVENING, Locale.JAPAN), is("こんばんは"));
    }

    @Test
    public void getMessageWithMorningAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.MORNING, Locale.ENGLISH), is("Good Morning"));
    }

    @Test
    public void getMessageWithAfternoonAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.AFTERNOON, Locale.ENGLISH), is("Good Afternoon"));
    }

    @Test
    public void getMessageWithEveningAndEN() {
        Greeter greeter = new Greeter();
        assertThat(greeter.getMessage(Time.EVENING, Locale.ENGLISH), is("Good Evening"));
    }

    @Test
    public void greeterWithMorningAndJa() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(6, 0), Locale.JAPAN), is("おはようございます"));
    }

    @Test
    public void greeterWithAfternoonAndJa() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(12, 0), Locale.JAPAN), is("こんにちは"));
    }

    @Test
    public void greeterWithEveningAndJa() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(18, 0), Locale.JAPAN), is("こんばんは"));
    }

    @Test
    public void greeterWithMorningAndEn() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(6, 0), Locale.ENGLISH), is("Good Morning"));
    }

    @Test
    public void greeterWithAfternoonAndEn() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(12, 0), Locale.ENGLISH), is("Good Afternoon"));
    }

    @Test
    public void greeterWithEveningAndEn() {
        Greeter greeter = new Greeter();
        assertThat(greeter.greet(time(18, 0), Locale.ENGLISH), is("Good Evening"));
    }
}

Time.java

package pascal.orz.cn.sandbox.problem02;

/**
 *
 * @author koduki
 */
public enum Time {
    MORNING,
    AFTERNOON,
    EVENING
}