Document interfaces with @FunctionalInterface.

Javadoc.

src/main/java/org/apache/commons/lang3/builder/Builder.java

@@ -76,6 +76,7 @@ package org.apache.commons.lang3.builder;
  *
  * @since 3.0
  */
+@FunctionalInterface
 public interface Builder<T> {
 
     /**

src/main/java/org/apache/commons/lang3/builder/Diffable.java

@@ -39,6 +39,7 @@ package org.apache.commons.lang3.builder;
  * @param <T> the type of objects that this object may be differentiated against
  * @since 3.3
  */
+@FunctionalInterface
 public interface Diffable<T> {
 
     /**

src/main/java/org/apache/commons/lang3/reflect/TypeLiteral.java

@@ -69,6 +69,7 @@ import org.apache.commons.lang3.Validate;
  *   <T> T obtain(Typed<T> typed, ...);
  * </pre>
  *
+ * @param <T> the type
  * @since 3.2
  */
 public abstract class TypeLiteral<T> implements Typed<T> {

src/main/java/org/apache/commons/lang3/reflect/Typed.java

@@ -20,13 +20,16 @@ import java.lang.reflect.Type;
 
 /**
  * Generalization of "has a type."
+ *
+ * @param <T> the type
  * @see TypeLiteral
  * @since 3.2
  */
+@FunctionalInterface
 public interface Typed<T> {
 
     /**
-     * Get the {@link Type} represented by this entity.
+     * Gets the {@link Type} represented by this entity.
      *
      * @return Type
      */