Introduce dedicated LastGatherer class (#29)

pivovarit · Oct 14, 2024 · bb2798a · bb2798a
1 parent 30e8785
commit bb2798a
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Showing 2 changed files with 39 additions and 17 deletions.
diff --git a/src/main/java/com/pivovarit/gatherers/LastGatherer.java b/src/main/java/com/pivovarit/gatherers/LastGatherer.java
@@ -0,0 +1,38 @@
+package com.pivovarit.gatherers;
+
+import java.util.LinkedList;
+import java.util.function.BiConsumer;
+import java.util.function.Supplier;
+import java.util.stream.Gatherer;
+
+record LastGatherer<T>(long n) implements Gatherer<T, LinkedList<T>, T> {
+
+    LastGatherer {
+        if (n <= 0) {
+            throw new IllegalArgumentException("number of elements can't be lower than one");
+        }
+    }
+
+    @Override
+    public Supplier<LinkedList<T>> initializer() {
+        return LinkedList::new;
+    }
+
+    @Override
+    public Integrator<LinkedList<T>, T, T> integrator() {
+        return Integrator.ofGreedy((state, element, _) -> {
+            if (state.size() == n) {
+                state.removeFirst();
+                state.addLast(element);
+            } else {
+                state.addLast(element);
+            }
+            return true;
+        });
+    }
+
+    @Override
+    public BiConsumer<LinkedList<T>, Downstream<? super T>> finisher() {
+        return (state, downstream) -> state.forEach(downstream::push);
+    }
+}
diff --git a/src/main/java/com/pivovarit/gatherers/MoreGatherers.java b/src/main/java/com/pivovarit/gatherers/MoreGatherers.java
@@ -3,7 +3,6 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
-import java.util.LinkedList;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicLong;
@@ -22,22 +21,7 @@ private MoreGatherers() {
     }
 
     public static <T> Gatherer<T, ?, T> last(int n) {
-        if (n <= 0) {
-            throw new IllegalArgumentException("number of elements can't be lower than one");
-        }
-        return Gatherer.ofSequential(
-          () -> new LinkedList<T>(),
-          Integrator.ofGreedy((state, element, _) -> {
-              if (state.size() == n) {
-                  state.removeFirst();
-                  state.addLast(element);
-              } else {
-                  state.addLast(element);
-              }
-              return true;
-          }),
-          (state, downstream) -> state.forEach(downstream::push)
-        );
+        return new LastGatherer<>(n);
     }
 
     public static <T> Gatherer<T, ?, T> sample(int n) {