content: /*
   * 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.kafka.common.cache;
  
  /**
   * Interface for caches, semi-persistent maps which store key-value mappings until either an eviction criteria is met
   * or the entries are manually invalidated. Caches are not required to be thread-safe, but some implementations may be.
   */
  public interface Cache<K, V> {
  
      /**
       * Look up a value in the cache.
       * @param key the key to
       * @return the cached value, or null if it is not present.
       */
      V get(K key);
  
      /**
       * Insert an entry into the cache.
       * @param key the key to insert
       * @param value the value to insert
       */
      void put(K key, V value);
  
      /**
       * Manually invalidate a key, clearing its entry from the cache.
       * @param key the key to remove
       * @return true if the key existed in the cache and the entry was removed or false if it was not present
       */
      boolean remove(K key);
  
      /**
       * Get the number of entries in this cache. If this cache is used by multiple threads concurrently, the returned
       * value will only be approximate.
       * @return the number of entries in the cache
       */
      long size();
  }
  