1 /*
   2  * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /**
  27  * This package contains classes for consuming Flight Recorder data.
  28  * <p>
  29  * In the following example, the program prints a histogram of all method samples in a recording.
  30  * <pre>
  31  * <code>
  32  *   public static void main(String[] args) {
  33  *     if (args.length != 0) {
  34  *       System.out.println("Must specify recording file.");
  35  *       return;
  36  *     }
  37  *     try (RecordingFile f = new RecordingFile(Paths.get(args[0]))) {
  38  *       Map{@literal <}String, SimpleEntry{@literal <}String, Integer{@literal >}{@literal >} histogram = new HashMap{@literal <}{@literal >}();
  39  *       int total = 0;
  40  *       while (f.hasMoreEvents()) {
  41  *         RecordedEvent event = f.readEvent();
  42  *         if (event.getEventType().getName().equals("com.oracle.jdk.ExecutionSample")) {
  43  *           RecordedStackTrace s = event.getStackTrace();
  44  *           if (s != null) {
  45  *             RecordedFrame topFrame= s.getFrames().get(0);
  46  *             if (topFrame.isJavaFrame())  {
  47  *               RecordedMethod method = topFrame.getMethod();
  48  *               String methodName = method.getType().getName() + "#" + method.getName() + " " + method.getDescriptor();
  49  *               Entry entry = histogram.computeIfAbsent(methodName, u -{@literal >} new SimpleEntry{@literal <}String, Integer{@literal >}(methodName, 0));
  50  *               entry.setValue(entry.getValue() + 1);
  51  *               total++;
  52  *             }
  53  *           }
  54  *         }
  55  *       }
  56  *       List{@literal <}SimpleEntry{@literal <}String, Integer{@literal >}{@literal >} entries = new ArrayList{@literal <}{@literal >}(histogram.values());
  57  *       entries.sort((u, v) -{@literal >} v.getValue().compareTo(u.getValue()));
  58  *       for (SimpleEntry{@literal <}String, Integer{@literal >} c : entries) {
  59  *         System.out.printf("%2.0f%% %s\n", 100 * (float) c.getValue() / total, c.getKey());
  60  *       }
  61  *       System.out.println("\nSample count: " + total);
  62  *     } catch (IOException ioe) {
  63  *       System.out.println("Error reading file " + args[0] + ". " + ioe.getMessage());
  64  *     }
  65  *   }
  66  * </code>
  67  * </pre>
  68  * <p>
  69  * <b>Null-handling</b>
  70  * <p>
  71  * All methods define whether they accept or return {@code null} in the Javadoc.
  72  * Typically this is expressed as {@code "not null"}. If a {@code null}
  73  * parameter is used where it is not allowed, a
  74  * {@code java.lang.NullPointerException} is thrown. If a {@code null}
  75  * parameters is passed to a method that throws other exceptions, such as
  76  * {@code java.io.IOException}, the {@code java.lang.NullPointerException} takes
  77  * precedence, unless the Javadoc for the method explicitly states how
  78  * {@code null} is handled, i.e. by throwing {@code java.lang.IllegalArgumentException}.
  79  *
  80  * @commercialFeature
  81  * @since 9
  82  */
  83 package jdk.jfr.consumer;