More comments... a lot more!

src/main/java/me/clip/placeholderapi/expansion/Configurable.java

@@ -24,7 +24,7 @@ import java.util.Map;
 
 /**
  * Any {@link PlaceholderExpansion} class which implements configurable will have any options listed
- * in the getDefaults map automatically added to the PlaceholderAPI config.yml file
+ * in the {@link #getDefaults()} map automatically added to the PlaceholderAPI config.yml file
  *
  * @author Ryan McCarthy
  */

src/main/java/me/clip/placeholderapi/expansion/PlaceholderExpansion.java

@@ -32,10 +32,17 @@ import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+/**
+ * Any class extending this will be able to get registered as a PlaceholderExpansion.
+ * <br>The registration either happens automatically when the jar file containing a
+ * class extending this one is located under the {@code PlaceholderAPI/expansions}
+ * directory or when the {@link #register()} method is called by said class.
+ */
 public abstract class PlaceholderExpansion extends PlaceholderHook {
 
   /**
-   * The placeholder identifier of this expansion
+   * The placeholder identifier of this expansion. May not contain {@literal %},
+   * {@literal {}} or _
    *
    * @return placeholder identifier that is associated with this expansion
    */
@@ -153,58 +160,139 @@ public abstract class PlaceholderExpansion extends PlaceholderHook {
   }
 
   // === Configuration ===
-
+  
+  /**
+   * Gets the ConfigurationSection of the expansion located in the config.yml of PlaceholderAPI or
+   * null when not specified.
+   * <br>You may use the {@link Configurable} interface to define default values set
+   * 
+   * @return ConfigurationSection that this epxpansion has.
+   */
   @Nullable
   public final ConfigurationSection getConfigSection() {
     return getPlaceholderAPI().getConfig().getConfigurationSection("expansions." + getIdentifier());
   }
-
+  
+  /**
+   * Gets the ConfigurationSection relative to the {@link #getConfigSection() default one} set
+   * by the expansion or null when the default ConfigurationSection is null
+   * 
+   * @param path The path to get the ConfigurationSection from. This is relative to the default section
+   * @return ConfigurationSection relative to the default section
+   */
   @Nullable
   public final ConfigurationSection getConfigSection(@NotNull final String path) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? null : section.getConfigurationSection(path);
   }
-
+  
+  /**
+   * Gets the Object relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or the provided Default Object, when the default ConfigurationSection is null
+   * 
+   * @param path The path to get the Object from. This is relative to the default section
+   * @param def The default Object to return when the ConfigurationSection returns null
+   * @return Object from the provided path or the default one provided
+   */
   @Nullable
   @Contract("_, !null -> !null")
   public final Object get(@NotNull final String path, final Object def) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? def : section.get(path, def);
   }
-
+  
+  /**
+   * Gets the int relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or the provided Default int, when the default ConfigurationSection is null
+   *
+   * @param path The path to get the int from. This is relative to the default section
+   * @param def The default int to return when the ConfigurationSection returns null
+   * @return int from the provided path or the default one provided
+   */
   public final int getInt(@NotNull final String path, final int def) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? def : section.getInt(path, def);
   }
-
+  
+  /**
+   * Gets the long relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or the provided Default long, when the default ConfigurationSection is null
+   *
+   * @param path The path to get the long from. This is relative to the default section
+   * @param def The default long to return when the ConfigurationSection returns null
+   * @return long from the provided path or the default one provided
+   */
   public final long getLong(@NotNull final String path, final long def) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? def : section.getLong(path, def);
   }
-
+  
+  /**
+   * Gets the double relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or the provided Default double, when the default ConfigurationSection is null
+   *
+   * @param path The path to get the double from. This is relative to the default section
+   * @param def The default double to return when the ConfigurationSection returns null
+   * @return double from the provided path or the default one provided
+   */
   public final double getDouble(@NotNull final String path, final double def) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? def : section.getDouble(path, def);
   }
-
+  
+  /**
+   * Gets the String relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or the provided Default String, when the default ConfigurationSection is null
+   *
+   * @param path The path to get the String from. This is relative to the default section
+   * @param def The default String to return when the ConfigurationSection returns null. Can be null
+   * @return String from the provided path or the default one provided
+   */
   @Nullable
   @Contract("_, !null -> !null")
   public final String getString(@NotNull final String path, @Nullable final String def) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? def : section.getString(path, def);
   }
-
+  
+  /**
+   * Gets a String List relative to the {@link #getConfigSection() default ConfigurationSection} set
+   * by the expansion or an empty List, when the default ConfigurationSection is null
+   *
+   * @param path The path to get the String list from. This is relative to the default section
+   * @return String list from the provided path or an empty list
+   */
   @NotNull
   public final List<String> getStringList(@NotNull final String path) {
     final ConfigurationSection section = getConfigSection();
     return section == null ? Collections.emptyList() : section.getStringList(path);
   }
-
+  
+  /**
+   * Whether the {@link #getConfigSection() default ConfigurationSection} contains the provided path
+   * or not. This will return {@code false} when either the default section is null, or doesn't
+   * contain the provided path
+   *
+   * @param path The path to check
+   * @return true when the default ConfigurationSection is not null and contains the path, false otherwise
+   */
   public final boolean configurationContains(@NotNull final String path) {
     final ConfigurationSection section = getConfigSection();
     return section != null && section.contains(path);
   }
-
+  
+  /**
+   * Whether the provided Object is an instance of this PlaceholderExpansion.
+   * <br>This method will perform the following checks in order:
+   * <br><ul>
+   *     <li>Checks if Object equals the class. Returns true when equal and continues otherwise</li>
+   *     <li>Checks if the Object is an instance of a PlaceholderExpansion. Returns false if not</li>
+   *     <li>Checks if the Object's Identifier, Author and version equal the one of this class</li>
+   * </ul>
+   * 
+   * @param o The Object to check
+   * @return true or false depending on the above mentioned checks
+   */
   @Override
   public final boolean equals(final Object o) {
     if (this == o) {
@@ -220,7 +308,12 @@ public abstract class PlaceholderExpansion extends PlaceholderHook {
         getAuthor().equals(expansion.getAuthor()) &&
         getVersion().equals(expansion.getVersion());
   }
-
+  
+  /**
+   * Returns a String containing the Expansion's name, author and version
+   * 
+   * @return String containing name, author and version of the expansion
+   */
   @Override
   public final String toString() {
     return String.format("PlaceholderExpansion[name: '%s', author: '%s', version: '%s']", getName(),