1 files changed, 33 insertions, 0 deletions
diff --git a/src/main/java/org/javacs/LruCache.java b/src/main/java/org/javacs/LruCache.java
new file mode 100644
index 0000000..5f82388
--- /dev/null
+++ b/src/main/java/org/javacs/LruCache.java
@@ -0,0 +1,33 @@
+package org.javacs;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.function.Function;
+
+class LruCache<K, V> {
+    private final ArrayBlockingQueue<K> fifo;
+    private final Map<K, V> map;
+    private final Function<K, V> loader;
+
+    LruCache(int capacity, Function<K, V> loader) {
+        this.fifo = new ArrayBlockingQueue<>(capacity);
+        this.map = new HashMap<K, V>(capacity);
+        this.loader = loader;
+    }
+
+    public V get(K key) {
+        // If we already have key in cache, return it
+        if (map.containsKey(key)) return map.get(key);
+        // If we need to make room for another entry, remove the oldest entry
+        if (fifo.remainingCapacity() == 0) {
+            var evict = fifo.remove();
+            map.remove(evict);
+        }
+        // Add key to map
+        map.put(key, loader.apply(key));
+        fifo.add(key);
+
+        return map.get(key);
+    }
+}