--- /dev/null 2016-08-11 12:49:21.000000000 -0400 +++ new/test/lib/jdk/test/lib/DynamicVMOption.java 2016-08-11 12:49:21.369074700 -0400 @@ -0,0 +1,165 @@ +/* + * Copyright (c) 2014, 2015, 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. + * + * 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. + */ +package jdk.test.lib; + +import com.sun.management.HotSpotDiagnosticMXBean; +import java.lang.management.ManagementFactory; + +/** + * A utility class to work with VM options which could be altered during + * execution. + * + * This class is a wrapper around {@code com.sun.management.VMOption}. + * It provides more convenient interface to read/write the values. + * + */ +public class DynamicVMOption { + + private final HotSpotDiagnosticMXBean mxBean; + + /** + * VM option name, like "MinHeapFreeRatio". + */ + public final String name; + + /** + * Creates an instance of DynamicVMOption. + * + * @param name the VM option name + */ + public DynamicVMOption(String name) { + this.name = name; + mxBean = ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class); + } + + /** + * Sets a new value for the option. + * Trying to set not applicable value will cause IllegalArgumentException. + * Behavior with null is undefined, most likely NPE will be thrown. + * + * @param newValue the value to be set + * @see #getValue() + * @throws IllegalArgumentException if newValue is not applicable to the option + */ + public final void setValue(String newValue) { + mxBean.setVMOption(name, newValue); + } + + /** + * Returns the value of option. + * + * @return the current option value + * @see #setValue(java.lang.String) + */ + public final String getValue() { + return mxBean.getVMOption(name).getValue(); + } + + /** + * Returns true, if option is writable, false otherwise. + * + * @return true, if option is writable, false otherwise + */ + public final boolean isWriteable() { + return mxBean.getVMOption(name).isWriteable(); + } + + /** + * Checks if the given value is applicable for the option. + * + * This method tries to set the option to the new value. If no exception + * has been thrown the value is treated as valid. + * + * Calling this method will not change the option value. After an attempt + * to set a new value, the option will be restored to its previous value. + * + * @param value the value to verify + * @return true if option could be set to the given value + */ + public boolean isValidValue(String value) { + boolean isValid = true; + String oldValue = getValue(); + try { + setValue(value); + } catch (NullPointerException e) { + if (value == null) { + isValid = false; + } + } catch (IllegalArgumentException e) { + isValid = false; + } finally { + setValue(oldValue); + } + return isValid; + } + + /** + * Returns the value of the given VM option as String. + * + * This is a simple shortcut for {@code new DynamicVMOption(name).getValue()} + * + * @param name the name of VM option + * @return value as a string + * @see #getValue() + */ + public static String getString(String name) { + return new DynamicVMOption(name).getValue(); + } + + /** + * Returns the value of the given option as int. + * + * @param name the name of VM option + * @return value parsed as integer + * @see #getString(java.lang.String) + * + */ + public static int getInt(String name) { + return Integer.parseInt(getString(name)); + } + + /** + * Sets the VM option to a new value. + * + * This is a simple shortcut for {@code new DynamicVMOption(name).setValue(value)} + * + * @param name the name of VM option + * @param value the value to be set + * @see #setValue(java.lang.String) + */ + public static void setString(String name, String value) { + new DynamicVMOption(name).setValue(value); + } + + /** + * Sets the VM option value to a new integer value. + * + * @param name the name of VM option + * @param value the integer value to be set + * @see #setString(java.lang.String, java.lang.String) + */ + public static void setInt(String name, int value) { + new DynamicVMOption(name).setValue(Integer.toString(value)); + } + +}