src/jdk.jfr/share/classes/jdk/jfr/consumer/package-info.java
author egahlin
Wed, 18 Sep 2019 08:20:10 +0200
branchJEP-349-branch
changeset 58201 2654d1b665bf
parent 53016 9f13f8aad8dc
permissions -rw-r--r--
Javadoc change

/*
 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/**
 * This package contains classes for consuming Flight Recorder data.
 * <p>
 * In the following example, the program prints a histogram of all method samples in a recording.
 * <pre>
 * <code>
 * public static void main(String[] args) throws IOException {
 *     if (args.length != 1) {
 *         System.err.println("Must specify a recording file.");
 *         return;
 *     }
 *
 *     RecordingFile.readAllEvents(Path.of(args[0])).stream()
 *         .filter(e -> e.getEventType().getName().equals("jdk.ExecutionSample"))
 *         .map(e -> e.getStackTrace())
 *         .filter(s -> s != null)
 *         .map(s -> s.getFrames().get(0))
 *         .filter(f -> f.isJavaFrame())
 *         .map(f -> f.getMethod())
 *         .collect(
 *             Collectors.groupingBy(m -> m.getType().getName() + "." + m.getName() + " " + m.getDescriptor(),
 *             Collectors.counting()))
 *         .entrySet()
 *         .stream()
 *         .sorted((a, b) -> b.getValue().compareTo(a.getValue()))
 *         .forEach(e -> System.out.printf("%8d %s\n", e.getValue(), e.getKey()));
 * }
 * </code>
 * </pre>
 * <p>
 * <b>Null-handling</b>
 * <p>
 * All methods define whether they accept or return {@code null} in the Javadoc.
 * Typically this is expressed as {@code "not null"}. If a {@code null}
 * parameter is used where it is not allowed, a
 * {@code java.lang.NullPointerException} is thrown. If a {@code null}
 * parameters is passed to a method that throws other exceptions, such as
 * {@code java.io.IOException}, the {@code java.lang.NullPointerException} takes
 * precedence, unless the Javadoc for the method explicitly states how
 * {@code null} is handled, i.e. by throwing {@code java.lang.IllegalArgumentException}.
 *
 * @since 9
 */
package jdk.jfr.consumer;