solr/solrj/src/java/org/apache/solr/common/util/Cache.java

/*
 * 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.solr.common.util;

import java.util.Objects;
import java.util.function.Function;

public interface Cache<K, V> {
  V put(K key, V val);

  V get(K key);

  V remove(K key);

  void clear();

  default V computeIfAbsent(K key,
                            Function<? super K, ? extends V> mappingFunction) {
    Objects.requireNonNull(mappingFunction);
    V v;
    if ((v = get(key)) == null) {
      V newValue;
      if ((newValue = mappingFunction.apply(key)) != null) {
        put(key, newValue);
        return newValue;
      }
    }

    return v;
  }

}