optimize Acc#combine

Author: h908714124

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

@@ -72,11 +72,14 @@ public Set<Characteristics> characteristics() {
 
     // visible for testing
     static abstract class Acc<L, C, R> {
-        private List<R> right;
+        private ArrayList<R> right;
 
-        final List<R> right() {
-            return right == null ? List.of() : right;
-        }
+        abstract void combineLeft(C otherLeft);
+
+        abstract boolean isLeft();
+
+        /** Returns {@code null} iff {@link #isLeft()} */
+        abstract C left();
 
         final void addRight(R value) {
             if (isLeft()) {
@@ -100,23 +103,17 @@ final Acc<L, C, R> combine(Acc<L, C, R> other) {
                 return this;
             }
             if (right == null) {
-                right = new ArrayList<>();
+                right = other.right;
+            } else {
+                right.addAll(other.right);
             }
-            right.addAll(other.right);
             return this;
         }
 
-        abstract void combineLeft(C otherLeft);
-
-        abstract boolean isLeft();
-
-        abstract C left();
-
-        Either<C, List<R>> finish() {
-            if (isLeft()) {
-                return Either.left(left());
-            }
-            return Either.right(right());
+        final Either<C, List<R>> finish() {
+            return isLeft()
+                    ? Either.left(left())
+                    : Either.right(right == null ? List.of() : right);
         }
     }
 
@@ -149,7 +146,9 @@ private static class FullAcc<L, R> extends Acc<L, List<L>, R> {
 
         @Override
         void combineLeft(List<L> otherLeft) {
-            if (otherLeft != null && !otherLeft.isEmpty()) {
+            if (left == null) {
+                left = otherLeft;
+            } else if (otherLeft != null && !otherLeft.isEmpty()) {
                 left.addAll(otherLeft);
             }
         }

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

@@ -1,6 +1,5 @@
 package io.jbock.util;
 
-import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -114,6 +113,6 @@ public boolean equals(Object obj) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(value);
+        return value.hashCode();
     }
 }