* Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.

import static java.util.Collections.emptyList;

import static java.util.Collections.unmodifiableList;

import static java.util.Objects.requireNonNull;

 * <p> The methods of this class ( that accept a String header name ), and the

 * Map returned by the {@linkplain #map() map} method, operate without regard to

 * case when retrieving the header value.

 *

 * <p> HttpHeaders instances are immutable.

 *

public abstract class HttpHeaders {

    /**

     * Creates an HttpHeaders.

     */

    protected HttpHeaders() {}

     * Returns an {@link Optional} containing the first value of the given named

     * (and possibly multi-valued) header. If the header is not present, then

     * the returned {@code Optional} is empty.

     *

     * @implSpec

     * The default implementation invokes

     * {@code allValues(name).stream().findFirst()}

    public Optional<String> firstValue(String name) {

        return allValues(name).stream().findFirst();

    }

     * Returns an {@link OptionalLong} containing the first value of the

     * named header field. If the header is not present, then the Optional is

     * empty. If the header is present but contains a value that does not parse

     * as a {@code Long} value, then an exception is thrown.

     *

     * @implSpec

     * The default implementation invokes

     * {@code allValues(name).stream().mapToLong(Long::valueOf).findFirst()}

    public OptionalLong firstValueAsLong(String name) {

        return allValues(name).stream().mapToLong(Long::valueOf).findFirst();

    }

     * @implSpec

     * The default implementation invokes, among other things, the

     * {@code map().get(name)} to retrieve the list of header values.

     *

    public List<String> allValues(String name) {

        requireNonNull(name);

        List<String> values = map().get(name);

        // Making unmodifiable list out of empty in order to make a list which

        // throws UOE unconditionally

        return values != null ? values : unmodifiableList(emptyList());

    }

     * Returns an unmodifiable multi Map view of this HttpHeaders.

    public abstract Map<String, List<String>> map();

    /**

     * Tests this HTTP headers instance for equality with the given object.

     *

     * <p> If the given object is not an {@code HttpHeaders} then this

     * method returns {@code false}. Two HTTP headers are equal if each

     * of their corresponding {@linkplain #map() maps} are equal.

     *

     * <p> This method satisfies the general contract of the {@link

     * Object#equals(Object) Object.equals} method.

     *

     * @param obj the object to which this object is to be compared

     * @return {@code true} if, and only if, the given object is an {@code

     *         HttpHeaders} that is equal to this HTTP headers

     */

    public final boolean equals(Object obj) {

        if (!(obj instanceof HttpHeaders))

            return false;

        HttpHeaders that = (HttpHeaders)obj;

        return this.map().equals(that.map());

    }

    /**

     * Computes a hash code for this HTTP headers instance.

     *

     * <p> The hash code is based upon the components of the HTTP headers

     * {@linkplain #map() map}, and satisfies the general contract of the

     * {@link Object#hashCode Object.hashCode} method.

     *

     * @return the hash-code value for this HTTP headers

     */

    public final int hashCode() {

        return map().hashCode();

    }

    /**

     * Returns this HTTP headers as a string.

     *

     * @return a string describing the HTTP headers

     */

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        sb.append(super.toString()).append(" ");

        sb.append(map());

        sb.append(" }");

        return sb.toString();

    }