Added javadocs and refactoring.

src/main/java/com/github/prominence/openweathermap/api/annotation/SubscriptionAvailability.java

@@ -29,6 +29,9 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+/**
+ * Marker-type annotation to specify what type of license it needs to have to use API method.
+ */
 @Target(ElementType.METHOD)
 @Retention(RetentionPolicy.CLASS)
 public @interface SubscriptionAvailability {

src/main/java/com/github/prominence/openweathermap/api/enums/Language.java

@@ -22,8 +22,11 @@
 
 package com.github.prominence.openweathermap.api.enums;
 
+/**
+ * An enumeration which lists all available languages for API usage.
+ * Usually it could be specified to get response with some fields translated into desired language.
+ */
 public enum Language {
-
     ARABIC("ar"),
     BULGARIAN("bg"),
     CATALAN("ca"),

src/main/java/com/github/prominence/openweathermap/api/enums/SubscriptionPlan.java

@@ -22,6 +22,10 @@
 
 package com.github.prominence.openweathermap.api.enums;
 
+/**
+ * An enumeration with all available subscription plans.
+ * More information <a href="https://openweathermap.org/price">at official website</a>.
+ */
 public enum SubscriptionPlan {
     FREE,
     STARTUP,

src/main/java/com/github/prominence/openweathermap/api/enums/TimeFrame.java

@@ -22,6 +22,7 @@
 
 package com.github.prominence.openweathermap.api.enums;
 
+@Deprecated
 public enum TimeFrame {
     YEAR,
     MONTH,

src/main/java/com/github/prominence/openweathermap/api/enums/UnitSystem.java

@@ -22,8 +22,10 @@
 
 package com.github.prominence.openweathermap.api.enums;
 
+/**
+ * An enumeration for supported unit systems with helper methods.
+ */
 public enum UnitSystem {
-
     METRIC("metric"),
     IMPERIAL("imperial"),
     STANDARD("standard");
@@ -34,8 +36,8 @@ public enum UnitSystem {
         this.value = value;
     }
 
-    public static String getWindUnit(UnitSystem type) {
+    public String getWindUnit() {
-        switch (type) {
+        switch (this) {
             case IMPERIAL:
                 return "miles/hour";
             case STANDARD:
@@ -45,8 +47,8 @@ public enum UnitSystem {
         }
     }
 
-    public static String getTemperatureUnit(UnitSystem type) {
+    public String getTemperatureUnit() {
-        switch (type) {
+        switch (this) {
             case METRIC:
                 return "℃";
             case IMPERIAL:

src/main/java/com/github/prominence/openweathermap/api/exception/InvalidAuthTokenException.java

@@ -22,10 +22,13 @@
 
 package com.github.prominence.openweathermap.api.exception;
 
+/**
+ * An exception that could be thrown in case of your API key is invalid or your subscription plan does not cover requested functionality.
+ * Subscription plans information you can find <a href="https://openweathermap.org/price">here</a>.
+ * API Keys could be checked in <a href="https://home.openweathermap.org/api_keys/">your profile</a>.
+ */
 public class InvalidAuthTokenException extends RuntimeException {
-
     public InvalidAuthTokenException() {
         super("Authentication token wasn't set or requested functionality is not permitted for your subscription plan. Please, check https://home.openweathermap.org/api_keys/ and https://openweathermap.org/price.");
     }
-
 }

src/main/java/com/github/prominence/openweathermap/api/exception/NoDataFoundException.java

@@ -22,8 +22,15 @@
 
 package com.github.prominence.openweathermap.api.exception;
 
+/**
+ * An exception that could be thrown in several cases:
+ * <ul>
+ *     <li>There is no data found for your query(wrong coordinates somewhere in the sea, some distant place, etc.);</li>
+ *     <li>Request is malformed. An occasion to report an <a href="https://github.com/Prominence/openweathermap-java-api/issues">issue</a>;</li>
+ *     <li>Any other unpredictable problems.</li>
+ * </ul>
+ */
 public class NoDataFoundException extends RuntimeException {
-
     public NoDataFoundException() {
         super("Data for provided parameters wasn't found. Please, check requested location.");
     }
@@ -31,5 +38,4 @@ public class NoDataFoundException extends RuntimeException {
     public NoDataFoundException(Throwable throwable) {
         super(throwable.getMessage(), throwable.getCause());
     }
-
 }

src/main/java/com/github/prominence/openweathermap/api/request/forecast/free/FiveDayThreeHourStepForecastResponseMapper.java

@@ -151,7 +151,7 @@ public class FiveDayThreeHourStepForecastResponseMapper {
 
     private Temperature parseTemperature(JsonNode rootNode) {
         final double tempValue = rootNode.get("temp").asDouble();
-        Temperature temperature = Temperature.forValue(tempValue, UnitSystem.getTemperatureUnit(unitSystem));
+        Temperature temperature = Temperature.forValue(tempValue, unitSystem.getTemperatureUnit());
 
         final JsonNode tempMaxNode = rootNode.get("temp_max");
         if (tempMaxNode != null) {
@@ -192,7 +192,7 @@ public class FiveDayThreeHourStepForecastResponseMapper {
         final JsonNode windNode = root.get("wind");
         double speed = windNode.get("speed").asDouble();
 
-        Wind wind = Wind.forValue(speed, UnitSystem.getWindUnit(unitSystem));
+        Wind wind = Wind.forValue(speed, unitSystem.getWindUnit());
         final JsonNode degNode = windNode.get("deg");
         if (degNode != null) {
             wind.setDegrees(degNode.asDouble());

src/main/java/com/github/prominence/openweathermap/api/request/weather/CurrentWeatherResponseMapper.java

@@ -147,7 +147,7 @@ public class CurrentWeatherResponseMapper implements ResponseMapper<Weather> {
         final JsonNode mainNode = rootNode.get("main");
 
         final double tempValue = mainNode.get("temp").asDouble();
-        temperature = Temperature.forValue(tempValue, UnitSystem.getTemperatureUnit(unitSystem));
+        temperature = Temperature.forValue(tempValue, unitSystem.getTemperatureUnit());
 
         final JsonNode feelsLikeNode = mainNode.get("feels_like");
         if (feelsLikeNode != null) {
@@ -191,7 +191,7 @@ public class CurrentWeatherResponseMapper implements ResponseMapper<Weather> {
         final JsonNode windNode = rootNode.get("wind");
         double speed = windNode.get("speed").asDouble();
 
-        Wind wind = Wind.forValue(speed, UnitSystem.getWindUnit(unitSystem));
+        Wind wind = Wind.forValue(speed, unitSystem.getWindUnit());
 
         final JsonNode degNode = windNode.get("deg");
         if (degNode != null) {

src/main/java/com/github/prominence/openweathermap/api/utils/RequestUtils.java

@@ -53,7 +53,6 @@ public final class RequestUtils {
      * @return <code>InputStream</code> instance containing http response body.
      * @throws InvalidAuthTokenException in case if authentication token wasn't set or requested functionality is not permitted for its subscription plan.
      * @throws NoDataFoundException in case if there is no any data for requested location(s) or request is invalid.
-     * @throws IllegalStateException in case of unexpected response or error.
      */
     private static InputStream executeRequest(URL requestUrl) {
         InputStream resultStream;