Commonize no value exceptions

2bllw8 · Sep 9, 2021 · a975e63 · a975e63
1 parent 8e935ec
commit a975e63
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Showing 3 changed files with 18 additions and 11 deletions.
diff --git a/lib/src/main/java/exe/bbllw8/either/Either.java b/lib/src/main/java/exe/bbllw8/either/Either.java
@@ -6,6 +6,7 @@
 
 import java.util.Collection;
 import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Function;
@@ -17,7 +18,7 @@
  *
  * <code>null</code> values are not accepted and will throw exceptions
  * if used in an Either instance.
- *
+ * <p>
  * Construct an instance using one of:
  * <ul>
  *     <li>{@link #left(Object)}: instance with a left value</li>
@@ -33,15 +34,15 @@ public abstract class Either<L, R> {
 
     /**
      * Whether this either has a left value.
-     *
+     * <p>
      * If this is <code>true</code>, {@link #getRight()}
      * must be <code>false</code>.
      */
     public abstract boolean isLeft();
 
     /**
      * Whether this either has a right value.
-     *
+     * <p>
      * If this is <code>true</code>, {@link #getLeft()}
      * must be <code>false</code>.
      */
@@ -167,4 +168,12 @@ public static <L, R> Collection<R> rightValues(List<Either<L, R>> list) {
     public static <T> T reduce(Either<T, T> either) {
         return Objects.requireNonNull(either).either(Function.identity(), Function.identity());
     }
+
+    protected static NoSuchElementException noLeftValueException() {
+        return new NoSuchElementException("No left value present");
+    }
+
+    protected static NoSuchElementException noRightValueException() {
+        return new NoSuchElementException("No right value present");
+    }
 }
diff --git a/lib/src/main/java/exe/bbllw8/either/LeftEither.java b/lib/src/main/java/exe/bbllw8/either/LeftEither.java
@@ -4,7 +4,6 @@
  */
 package exe.bbllw8.either;
 
-import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Function;
@@ -34,18 +33,18 @@ public boolean isRight() {
 
     @Override
     public L getLeft() {
-        return left.orElseThrow(() -> new NoSuchElementException("No left value present"));
+        return left.orElseThrow(Either::noLeftValueException);
     }
 
     @Override
     public R getRight() {
-        throw new NoSuchElementException("No right value present");
+        throw noRightValueException();
     }
 
     @Override
     public <T> T either(Function<? super L, ? extends T> mapLeft,
                         Function<? super R, ? extends T> mapRight) {
-        return left.map(mapLeft).orElseThrow(() -> new NoSuchElementException("No left value present"));
+        return left.map(mapLeft).orElseThrow(Either::noLeftValueException);
     }
 
     @Override

diff --git a/lib/src/main/java/exe/bbllw8/either/RightEither.java b/lib/src/main/java/exe/bbllw8/either/RightEither.java
@@ -4,7 +4,6 @@
  */
 package exe.bbllw8.either;
 
-import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Function;
@@ -34,18 +33,18 @@ public boolean isRight() {
 
     @Override
     public L getLeft() {
-        throw new NoSuchElementException("No left value present");
+        throw noLeftValueException();
     }
 
     @Override
     public R getRight() {
-        return right.orElseThrow(() -> new NoSuchElementException("No right value present"));
+        return right.orElseThrow(Either::noRightValueException);
     }
 
     @Override
     public <T> T either(Function<? super L, ? extends T> mapLeft,
                         Function<? super R, ? extends T> mapRight) {
-        return right.map(mapRight).orElseThrow(() -> new NoSuchElementException("No right value present"));
+        return right.map(mapRight).orElseThrow(Either::noRightValueException);
     }
 
     @Override