Add Result.orElseThrow()

src/main/java/net/kemitix/mon/result/Err.java

@@ -67,4 +67,9 @@ class Err<T> implements Result<T> {
     public Result<Maybe<T>> maybe(final Predicate<T> predicate) {
         return Result.error(error);
     }
+
+    @Override
+    public T orElseThrow() throws Throwable {
+        throw error;
+    }
 }

src/main/java/net/kemitix/mon/result/Result.java

@@ -29,7 +29,7 @@ import java.util.function.Predicate;
 import java.util.function.Supplier;
 
 /**
- * An Either type for holding a result or an error (exception).
+ * An Either type for holding a result or an error (Throwable).
  *
  * @param <T> the type of the result when a success
  * @author Paul Campbell (pcampbell@kemitix.net)
@@ -44,7 +44,7 @@ public interface Result<T> {
      * @param <T>   the type of the Maybe and the Result
      * @return a Result containing the value of the Maybe when it is a Just, or the error when it is Nothing
      */
-    static <T> Result<T> fromMaybe(final Maybe<T> maybe, final Supplier<Exception> error) {
+    static <T> Result<T> fromMaybe(final Maybe<T> maybe, final Supplier<Throwable> error) {
         return maybe.map(Result::ok)
                 .orElseGet(() -> Result.error(error.get()));
     }
@@ -52,7 +52,7 @@ public interface Result<T> {
     /**
      * Create a Result for an error.
      *
-     * @param error the error (exception)
+     * @param error the error (Throwable)
      * @param <T>   the type had the result been a success
      * @return an error Result
      */
@@ -119,4 +119,12 @@ public interface Result<T> {
      */
     Result<Maybe<T>> maybe(Predicate<T> predicate);
 
+    /**
+     * Extracts the successful value from the result, or throws the error Throwable.
+     *
+     * @return the value if a success
+     * @throws Throwable the result is an error
+     */
+    @SuppressWarnings("illegalthrows")
+    T orElseThrow() throws Throwable;
 }

src/main/java/net/kemitix/mon/result/Success.java

@@ -70,4 +70,9 @@ class Success<T> implements Result<T> {
         }
         return Result.ok(Maybe.nothing());
     }
+
+    @Override
+    public T orElseThrow() {
+        return value;
+    }
 }

src/test/java/net/kemitix/mon/ResultTest.java

@@ -222,6 +222,26 @@ public class ResultTest implements WithAssertions {
         );
     }
 
+    @Test
+    public void success_whenOrElseThrow_isValue() throws Throwable {
+        //given
+        final Result<Integer> ok = Result.ok(1);
+        //when
+        final Integer value = ok.orElseThrow();
+        //then
+        assertThat(value).isEqualTo(1);
+    }
+
+    @Test
+    public void error_whenOrElseThrow_throws() {
+        //given
+        final RuntimeException exception = new RuntimeException();
+        final Result<Integer> error = Result.error(exception);
+        //when
+        assertThatThrownBy(() -> error.orElseThrow())
+                .isSameAs(exception);
+    }
+
     @Test
     public void useCase_whenOkay_thenReturnSuccess() {
         //given