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.arrow.flight;
  
  import java.util.Set;
  
  /** A set of metadata key value pairs for a call (request or response). */
  public interface CallHeaders {
    /** Get the value of a metadata key. If multiple values are present, then get the last one. */
    String get(String key);
  
    /** Get the value of a metadata key. If multiple values are present, then get the last one. */
    byte[] getByte(String key);
  
    /** Get all values present for the given metadata key. */
    Iterable<String> getAll(String key);
  
    /** Get all values present for the given metadata key. */
    Iterable<byte[]> getAllByte(String key);
  
    /**
     * Insert a metadata pair with the given value.
     *
     * <p>Duplicate metadata are permitted.
     */
    void insert(String key, String value);
  
    /**
     * Insert a metadata pair with the given value.
     *
     * <p>Duplicate metadata are permitted.
     */
    void insert(String key, byte[] value);
  
    /** Get a set of all the metadata keys. */
    Set<String> keys();
  
    /** Check whether the given metadata key is present. */
    boolean containsKey(String key);
  }
  