Added fromRight/fromLeft methods and unit tests

src/main/java/com/ceticamarco/lambdatonic/Either.java

@@ -63,4 +63,26 @@ public sealed interface Either<L, R> permits Left, Right {
      * @param <T> The return type of the <i>fn</i> function
      */
     <T> Either<L, T> map(Function<R, T> fn);
+
+    /**
+     * <p>
+     *     Returns the content of <i>Right</i> or a default value
+     *     <br /><br />
+     *     The default value must be of the same type of the <i>Right</i> value
+     * </p>
+     * @param defaultValue The default value to return if <i>Either</i> is <i>Left</i>
+     * @return The right value of <i>Either</i> or the default value
+     */
+    R fromRight(R defaultValue);
+
+    /**
+     * <p>
+     *     Returns the content of <i>Left</i> or a default value
+     *     <br /><br />
+     *     The default value must be of the same type of the <i>Left</i> value
+     * </p>
+     * @param defaultValue The default value to return if <i>Either</i> is <i>Right</i>
+     * @return The left value of <i>Either</i> or the default value
+     */
+    L fromLeft(L defaultValue);
 }

src/main/java/com/ceticamarco/lambdatonic/Left.java

@@ -31,4 +31,14 @@ public record Left<L, R>(L value) implements Either<L, R> {
     public <T> Either<L, T> map(Function<R, T> fn) {
         return new Left<>(this.value);
     }
+
+    @Override
+    public R fromRight(R defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public L fromLeft(L defaultValue) {
+        return this.value;
+    }
 }

src/main/java/com/ceticamarco/lambdatonic/Right.java

@@ -31,4 +31,14 @@ public record Right<L, R>(R value) implements Either<L, R> {
     public <T> Either<L, T> map(Function<R, T> fn) {
         return new Right<>(fn.apply(this.value));
     }
+
+    @Override
+    public R fromRight(R defaultValue) {
+        return this.value;
+    }
+
+    @Override
+    public L fromLeft(L defaultValue) {
+        return defaultValue;
+    }
 }

src/test/java/com/ceticamarco/lambdatonic/LeftTests.java

@@ -74,4 +74,14 @@ public class LeftTests {
 
         assertEquals(composition, FGMapped);
     }
+
+    @Test
+    public void testFromRightOnLeft() {
+        assertEquals(this.numEither.fromRight(-1), -1);
+    }
+
+    @Test
+    public void testFromLeftOnLeft() {
+        assertEquals(this.resEither.fromLeft(-1), 19);
+    }
 }

src/test/java/com/ceticamarco/lambdatonic/RightTests.java

@@ -74,4 +74,14 @@ public class RightTests {
 
         assertEquals(composition, FGMapped);
     }
+
+    @Test
+    public void testFromRightOnRight() {
+        assertEquals(this.numEither.fromRight(-1), 4);
+    }
+
+    @Test
+    public void testFromLeftOnRight() {
+        assertEquals(this.resEither.fromLeft(-1), -1);
+    }
 }