1 /*
   2  * Copyright (c) 2013, 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.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 package com.oracle.java.testlibrary;
  25 
  26 import sun.jvmstat.monitor.Monitor;
  27 
  28 /**
  29  * Represents a performance counter in the JVM.
  30  *
  31  * See http://openjdk.java.net/groups/hotspot/docs/Serviceability.html#bjvmstat
  32  * for more details about performance counters.
  33  */
  34 public class PerfCounter {
  35     private final Monitor monitor;
  36     private final String name;
  37 
  38     PerfCounter(Monitor monitor, String name) {
  39         this.monitor = monitor;
  40         this.name = name;
  41     }
  42 
  43     /**
  44      * Returns the value of this performance counter as a long.
  45      *
  46      * @return The long value of this performance counter
  47      * @throws RuntimeException If the value of the performance counter isn't a long
  48      */
  49     public long longValue() {
  50         Object value = monitor.getValue();
  51         if (value instanceof Long) {
  52             return ((Long) value).longValue();
  53         }
  54         throw new RuntimeException("Expected " + monitor.getName() + " to have a long value");
  55     }
  56 
  57     /**
  58      * Returns the name of the performance counter.
  59      *
  60      * @return The name of the performance counter.
  61      */
  62     public String getName() {
  63         return name;
  64     }
  65 
  66     @Override
  67     public String toString() {
  68         return name;
  69     }
  70 }