1 /*
   2  * Copyright (c) 2013, 2015, 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 import java.lang.management.RuntimeMXBean;
  25 import java.lang.management.ManagementFactory;
  26 import java.util.List;
  27 
  28 /**
  29  * This class provides access to the input arguments to the VM.
  30  */
  31 public class InputArguments {
  32     private static final List<String> args;
  33 
  34     static {
  35         RuntimeMXBean runtimeMxBean = ManagementFactory.getRuntimeMXBean();
  36         args = runtimeMxBean.getInputArguments();
  37     }
  38 
  39     /**
  40      * Returns true if {@code arg} is an input argument to the VM.
  41      *
  42      * This is useful for checking boolean flags such as -XX:+UseSerialGC or
  43      * -XX:-UsePerfData.
  44      *
  45      * @param arg The name of the argument.
  46      * @return {@code true} if the given argument is an input argument,
  47      *         otherwise {@code false}.
  48      */
  49     public static boolean contains(String arg) {
  50         return args.contains(arg);
  51     }
  52 
  53     /**
  54      * Returns true if {@code prefix} is the start of an input argument to the
  55      * VM.
  56      *
  57      * This is useful for checking if flags describing a quantity, such as
  58      * -XX:+MaxMetaspaceSize=100m, is set without having to know the quantity.
  59      * To check if the flag -XX:MaxMetaspaceSize is set, use
  60      * {@code InputArguments.containsPrefix("-XX:MaxMetaspaceSize")}.
  61      *
  62      * @param prefix The start of the argument.
  63      * @return {@code true} if the given argument is the start of an input
  64      *         argument, otherwise {@code false}.
  65      */
  66     public static boolean containsPrefix(String prefix) {
  67         for (String arg : args) {
  68             if (arg.startsWith(prefix)) {
  69                 return true;
  70             }
  71         }
  72         return false;
  73     }
  74 }