Add Maybe.isJust() and Maybe.isNothing()

CHANGELOG

@@ -4,6 +4,9 @@ CHANGELOG
 0.11.0
 
 * Rename `Result.maybeThen()` as `Result.flatMapMaybe()`
+* Add `Maybe.match(Consumer,Runnable)`
+* Add `Maybe.isJust()`
+* Add `Maybe.isNothing()`
 
 0.10.0
 ------

src/main/java/net/kemitix/mon/maybe/Just.java

@@ -44,6 +44,16 @@ final class Just<T> implements Maybe<T> {
 
     private final T value;
 
+    @Override
+    public boolean isJust() {
+        return true;
+    }
+
+    @Override
+    public boolean isNothing() {
+        return false;
+    }
+
     @Override
     public <R> Maybe<R> flatMap(final Function<T, Maybe<R>> f) {
         return f.apply(value);

src/main/java/net/kemitix/mon/maybe/Maybe.java

@@ -76,6 +76,20 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
         return just(value);
     }
 
+    /**
+     * Checks if the Maybe is a Just.
+     *
+     * @return true if the Maybe is a Just
+     */
+    boolean isJust();
+
+    /**
+     * Checks if the Maybe is Nothing.
+     *
+     * @return true if the Maybe is Nothing
+     */
+    boolean isNothing();
+
     /**
      * Monad binder maps the Maybe into another Maybe using the binder method f.
      *

src/main/java/net/kemitix/mon/maybe/Nothing.java

@@ -39,6 +39,16 @@ final class Nothing<T> implements Maybe<T> {
 
     static final Maybe<?> INSTANCE = new Nothing<>();
 
+    @Override
+    public boolean isJust() {
+        return false;
+    }
+
+    @Override
+    public boolean isNothing() {
+        return true;
+    }
+
     @Override
     public <R> Maybe<R> flatMap(final Function<T, Maybe<R>> f) {
         return Maybe.nothing();

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

@@ -134,14 +134,14 @@ public interface Result<T> extends Functor<T, Result<?>> {
     }
 
     /**
-     * Checks of the Result is an error.
+     * Checks if the Result is an error.
      *
      * @return true if the Result is an error.
      */
     boolean isError();
 
     /**
-     * Checks of the Result is a success.
+     * Checks if the Result is a success.
      *
      * @return true if the Result is a success.
      */

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

@@ -219,4 +219,44 @@ public class MaybeTest implements WithAssertions {
         assertThat(flag).isTrue();
     }
 
+    @Test
+    public void just_isJust_isTrue() {
+        //given
+        final Maybe<Integer> maybe = just(1);
+        //when
+        final boolean isJust = maybe.isJust();
+        //then
+        assertThat(isJust).isTrue();
+    }
+
+    @Test
+    public void just_isNothing_isFalse() {
+        //given
+        final Maybe<Integer> maybe = just(1);
+        //when
+        final boolean isNothing = maybe.isNothing();
+        //then
+        assertThat(isNothing).isFalse();
+    }
+
+    @Test
+    public void nothing_isJust_isFalse() {
+        //given
+        final Maybe<Object> maybe = nothing();
+        //when
+        final boolean isJust = maybe.isJust();
+        //then
+        assertThat(isJust).isFalse();
+    }
+
+    @Test
+    public void nothing_isNothing_isTrue() {
+        //given
+        final Maybe<Object> maybe = nothing();
+        //when
+        final boolean isNothing = maybe.isNothing();
+        //then
+        assertThat(isNothing).isTrue();
+    }
+
 }