add orElseThrow

src/main/java/io/jbock/util/Either.java

@@ -179,6 +179,18 @@ public abstract void ifLeftOrElse(
             Consumer<? super L> leftAction,
             Consumer<? super R> rightAction);
 
+    /**
+     * If this is a Right, returns the RHS value.
+     * Otherwise throws an exception produced by the exception supplying function.
+     *
+     * @param exceptionSupplier exception supplying function
+     * @param <X> type of the exception
+     * @return the RHS value, if this is a Right
+     * @throws X the result of applying {@code exceptionSupplier} to the LHS value, if this is a Left
+     */
+    public abstract <X extends Throwable> R orElseThrow(
+            Function<? super L, ? extends X> exceptionSupplier) throws X;
+
     /**
      * Returns {@code true} if this is a Left, otherwise {@code false}.
      *

src/main/java/io/jbock/util/Left.java

@@ -80,6 +80,11 @@ public void ifLeftOrElse(Consumer<? super L> leftAction, Consumer<? super R> rig
         leftAction.accept(value);
     }
 
+    @Override
+    public <X extends Throwable> R orElseThrow(Function<? super L, ? extends X> exceptionSupplier) throws X {
+        throw exceptionSupplier.apply(value);
+    }
+
     @Override
     public String toString() {
         return String.format("Left[%s]", value);

src/main/java/io/jbock/util/Right.java

@@ -80,6 +80,11 @@ public void ifLeftOrElse(Consumer<? super L> leftAction, Consumer<? super R> rig
         rightAction.accept(value);
     }
 
+    @Override
+    public <X extends Throwable> R orElseThrow(Function<? super L, ? extends X> exceptionSupplier) {
+        return value;
+    }
+
     @Override
     public String toString() {
         return String.format("Right[%s]", value);

src/test/java/io/jbock/util/EitherTest.java

@@ -3,12 +3,14 @@
 import com.google.common.testing.EqualsTester;
 import org.junit.jupiter.api.Test;
 
+import java.io.IOException;
 import java.util.Objects;
 import java.util.Optional;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class EitherTest {
@@ -106,7 +108,7 @@ void testFilterLeft() {
     }
 
     @Test
-    void testAccept() {
+    void testIfLeftOrElse() {
         String[] output = {"1"};
         Either<Integer, Integer> left = Either.left(1);
         left.ifLeftOrElse(l -> output[0] = "L", r -> output[0] = "R");
@@ -123,4 +125,13 @@ void testFold() {
         Either<String, Integer> right = Either.right(2);
         assertEquals("2", right.fold(Objects::toString, Objects::toString));
     }
+
+    @Test
+    void testOrElseThrow() {
+        Either<String, ?> left = Either.left("1");
+        IOException x = assertThrows(IOException.class, () -> left.orElseThrow(IOException::new));
+        assertEquals("1", x.getMessage());
+        Either<String, String> right = Either.right("2");
+        assertEquals("2", right.orElseThrow(IllegalArgumentException::new));
+    }
 }