Add peekError and peekSuccess methods

README.md

@@ -2,7 +2,7 @@ Result-type for Java
 ====================
 
 The project provides Result-type similar to Result-type in Rust that
-allows to return either successfull result or otherwise some kind of error.
+allows to return either successful result or otherwise some kind of error.
 
 In Java, the native way of reporting errors are exceptions, either checked or unchecked.
 You do not need Result-type most of the time in Java-code, where
@@ -13,7 +13,7 @@ Handling exception in such situations can be cumbersome and require a lot of boi
 Result-type and associated helper-classes help with exception handling and
 allow to write idiomatic functional code that can interact with methods that throw exceptions.
 
-Result-type provides a way to pass error enformation as a first-class value through
+Result-type provides a way to pass error information as a first-class value through
 the code written in functional style.
 Routines are provided for interoperability of normal code that uses exception and
 functional code that uses Result-type, so that exceptions can be caught and propagated as

src/main/java/com/github/sviperll/result4j/Result.java

@@ -116,7 +116,7 @@ public sealed interface Result<R, E> {
      * Produces function-object that transforms error-values of results.
      * <p>
      * Similarly to {@link Result#mapError(Function)},
-     * this method allows to apply a transformation to a error-value, associated with a result,
+     * this method allows to apply a transformation to an error-value, associated with a result,
      * to get a new result.
      * In contrast to {@link Result#mapError(Function)},
      * instead of applying the transformation to some particular result,
@@ -280,7 +280,7 @@ static <R, E> Result<R, E> error(E error) {
      * @param <R> type of successful result value
      * @param <E> type representing error-value
      * @param value {@code Optional}-value containing {@code Result}-value
-     * @return
+     * @return {@code Result}-value with {@code Optional} successful result value.
      */
     static <R, E> Result<Optional<R>, E> fromOptionalResult(
             Optional<Result<R, E>> value
@@ -305,7 +305,8 @@ static <R, E> Result<Optional<R>, E> fromOptionalResult(
      * @param <E> type representing error-value
      * @param optional {@code Optional}-value
      * @param error error value
-     * @return
+     * @return {@code Result}-value with {@code Optional} successful result value,
+     *      or given error value.
      */
     static <R, E> Result<R, E> fromOptional(Optional<R> optional, E error) {
         Optional<Result<R, E>> optionalResult = optional.map(Result::success);
@@ -325,7 +326,7 @@ static <R, E> Result<R, E> fromOptional(Optional<R> optional, E error) {
      *   the result of this method is exactly the same as provided argument.
      * </ul>
      *
-     * @param <U> type of a successful result of a successor
+     * @param <U> type of successful result of a successor
      * @param result successor result
      */
     <U> Result<U, E> andThen(Result<U, E> result);
@@ -342,15 +343,15 @@ static <R, E> Result<R, E> fromOptional(Optional<R> optional, E error) {
      *   the result of this method a new result with transformed value.
      * </ul>
      *
-     * @param <U> new type of a successful result value
+     * @param <U> new type of successful result value
      * @param transformation transformation to be applied to values
      */
     <U> Result<U, E> map(Function<? super R, ? extends U> transformation);
 
     /**
      * Transforms an error-value of this result, when this is an error.
      * <p>
-     * this method allows to apply a transformation to a error-value,
+     * this method allows to apply a transformation to an error-value,
      * associated with a result, to get a new result.
      * <ul>
      *   <li>When this result is an error, then
@@ -359,7 +360,7 @@ static <R, E> Result<R, E> fromOptional(Optional<R> optional, E error) {
      *   the result of this method the same successful result with the same value.
      * </ul>
      *
-     * @param <E1> new type of an error-value
+     * @param <E1> new type of error-value
      * @param transformation transformation to be applied to error-values
      */
     <E1> Result<R, E1> mapError(Function<? super E, ? extends E1> transformation);
@@ -387,21 +388,27 @@ static <R, E> Result<R, E> fromOptional(Optional<R> optional, E error) {
      * throws an exception, by creating exception instance from error-value.
      *
      * @param <X> type of thrown exception
-     * @param errorToExceptionConvertion function to convert error-value to an exception
+     * @param errorToExceptionConverter function to convert error-value to an exception
      * @return the value of this result, when it is a successful result
      * @throws X when this is an error result
      */
-    default <X extends Exception> R throwError(Function<? super E, X> errorToExceptionConvertion)
+    default <X extends Exception> R throwError(Function<? super E, X> errorToExceptionConverter)
             throws X {
         return switch (this) {
             case Success<R, E> success -> success.result;
-            case Error<R, E> error -> throw errorToExceptionConvertion.apply(error.error);
+            case Error<R, E> error -> throw errorToExceptionConverter.apply(error.error);
         };
     }
 
     /** Invokes given consumer for a successful result value. */
     void ifSuccess(Consumer<R> consumer);
 
+    /** Invokes given consumer for an error-value of this result, and returns the same result. */
+    Result<R, E> peekError(Consumer<E> consumer);
+
+    /** Invokes given consumer for a success-value of this result, and returns the same result. */
+    Result<R, E> peekSuccess(Consumer<R> consumer);
+
     /**
      * Transforms a value of this result, when this is a successful result.
      * <p>
@@ -415,7 +422,7 @@ default <X extends Exception> R throwError(Function<? super E, X> errorToExcepti
      *   the result of this method the result of applying transformation to the argument.
      * </ul>
      *
-     * @param <U> new type of a successful result value
+     * @param <U> new type of successful result value
      * @param transformation transformation to be applied to values
      */
     default <U> Result<U, E> flatMap(
@@ -473,6 +480,17 @@ public R recoverError(
         public void ifSuccess(Consumer<R> consumer) {
             consumer.accept(result);
         }
+
+        @Override
+        public Result<R, E> peekError(Consumer<E> consumer) {
+            return this;
+        }
+
+        @Override
+        public Result<R, E> peekSuccess(Consumer<R> consumer) {
+            consumer.accept(result);
+            return this;
+        }
     }
 
     record Error<R, E>(E error) implements Result<R, E> {
@@ -520,5 +538,16 @@ public R recoverError(
         @Override
         public void ifSuccess(Consumer<R> consumer) {
         }
+
+        @Override
+        public Result<R, E> peekError(Consumer<E> consumer) {
+            consumer.accept(error);
+            return this;
+        }
+
+        @Override
+        public Result<R, E> peekSuccess(Consumer<R> consumer) {
+            return this;
+        }
     }
 }