toCountMap

SimonBaars · SimonBaars · commit 97407416ce95 · 2022-12-18T07:30:46.000+01:00
diff --git a/src/main/java/com/sbaars/adventofcode/year19/util/LongCountMap.java b/src/main/java/com/sbaars/adventofcode/year19/util/LongCountMap.java
@@ -2,6 +2,11 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.function.BiConsumer;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
 import java.util.stream.Collectors;
 import java.util.stream.LongStream;
 
@@ -51,10 +56,11 @@ public void addAll(LongCountMap<K> amountPerCloneClassSize) {
     amountPerCloneClassSize.entrySet().stream().forEach(e -> this.increment(e.getKey(), e.getValue()));
   }
 
-  public void incrementAll(LongCountMap<K> input) {
+  public LongCountMap<K> incrementAll(LongCountMap<K> input) {
     for (Entry<K, Long> i : input.entrySet()) {
       increment(i.getKey(), i.getValue());
     }
+    return this;
   }
 
   public long sumValues() {
@@ -66,4 +72,12 @@ public static LongCountMap<Long> ofFrequencies(LongStream frequencies) {
     frequencies.forEach(lcm::increment);
     return lcm;
   }
+
+  public static<T> Collector<T, LongCountMap<T>, LongCountMap<T>> toCountMap() {
+    final Supplier<LongCountMap<T>> supplier = LongCountMap::new;
+    final BiConsumer<LongCountMap<T>, T> accumulator = LongCountMap::increment;
+    final BinaryOperator<LongCountMap<T>> combiner = LongCountMap::incrementAll;
+    final Function<LongCountMap<T>, LongCountMap<T>> finisher = LongCountMap::new;
+    return Collector.of(supplier, accumulator, combiner, finisher);
+  }
 }
