8019466: Fix doclint issues in java.util.function

Reviewed-by: briangoetz

src/share/classes/java/util/function/BinaryOperator.java

@@ -42,6 +42,7 @@ public interface BinaryOperator<T> extends BiFunction<T,T,T> {
      * Returns a {@link BinaryOperator} which returns the lesser of two elements
      * according to the specified {@code Comparator}
      *
+     * @param <T> the type of values to be compared and returned
      * @param  comparator a {@code Comparator} for comparing the two values
      * @return a {@code BinaryOperator} which returns the lesser of its operands,
      *         according to the supplied {@code Comparator}
@@ -56,6 +57,7 @@ public interface BinaryOperator<T> extends BiFunction<T,T,T> {
      * Returns a {@link BinaryOperator} which returns the greater of two elements
      * according to the specified {@code Comparator}
      *
+     * @param <T> the type of values to be compared and returned
      * @param  comparator a {@code Comparator} for comparing the two values
      * @return a {@code BinaryOperator} which returns the greater of its operands,
      *         according to the supplied {@code Comparator}

src/share/classes/java/util/function/Function.java

@@ -87,6 +87,7 @@ public interface Function<T, R> {
      * Returns a {@code Function} whose {@code apply} method returns its input.
      *
      * @param <T> the type of the input and output objects to the function
+     * @return a {@code Function} whose {@code apply} method returns its input
      */
     static <T> Function<T, T> identity() {
         return t -> t;

src/share/classes/java/util/function/UnaryOperator.java

@@ -40,6 +40,7 @@ public interface UnaryOperator<T> extends Function<T, T> {
     /**
      * Returns a unary operator that provides its input value as the result.
      *
+     * @param <T> the type of the input and output objects to the function
      * @return a unary operator that provides its input value as the result
      */
     static <T> UnaryOperator<T> identity() {