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java/org/apache/el/util/ConcurrentCache.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.el.util;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+import java.util.concurrent.ConcurrentHashMap;
+
+public final class ConcurrentCache<K,V> {
+
+    private final int size;
+
+    private final Map<K,V> eden;
+
+    private final Map<K,V> longterm;
+
+    public ConcurrentCache(int size) {
+        this.size = size;
+        this.eden = new ConcurrentHashMap<>(size);
+        this.longterm = new WeakHashMap<>(size);
+    }
+
+    public V get(K k) {
+        V v = this.eden.get(k);
+        if (v == null) {
+            synchronized (longterm) {
+                v = this.longterm.get(k);
+            }
+            if (v != null) {
+                this.eden.put(k, v);
+            }
+        }
+        return v;
+    }
+
+    public void put(K k, V v) {
+        if (this.eden.size() >= size) {
+            synchronized (longterm) {
+                this.longterm.putAll(this.eden);
+            }
+            this.eden.clear();
+        }
+        this.eden.put(k, v);
+    }
+}