/*

 * 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

 * particular file as subject to the "Classpath" exception as provided

 *

 * 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.

 *

 */

package java.lang.management;

/**

 * The management interface for the operating system on which

 * the Java virtual machine is running.

 *

 * <p> A Java virtual machine has a single instance of the implementation

 * class of this interface.  This instance implementing this interface is

 * an <a href="ManagementFactory.html#MXBean">MXBean</a>

 * that can be obtained by calling

 * the {@link ManagementFactory#getOperatingSystemMXBean} method or

 * from the {@link ManagementFactory#getPlatformMBeanServer

 * platform <tt>MBeanServer</tt>} method.

 *

 * <p>The <tt>ObjectName</tt> for uniquely identifying the MXBean for

 * the operating system within an MBeanServer is:

 * <blockquote>

 *    {@link ManagementFactory#OPERATING_SYSTEM_MXBEAN_NAME

 *      <tt>java.lang:type=OperatingSystem</tt>}

 * </blockquote>

 *

 * It can be obtained by calling the

 * {@link PlatformManagedObject#getObjectName} method.

 *

 * <p> This interface defines several convenient methods for accessing

 * system properties about the operating system on which the Java

 * virtual machine is running.

 *

 * @see ManagementFactory#getPlatformMXBeans(Class)

 * @see <a href="../../../javax/management/package-summary.html">

 *      JMX Specification.</a>

 * @see <a href="package-summary.html#examples">

 *      Ways to Access MXBeans</a>

 *

 * @author  Mandy Chung

 * @since   1.5

 */

public interface OperatingSystemMXBean extends PlatformManagedObject {

    /**

     * Returns the operating system name.

     * This method is equivalent to <tt>System.getProperty("os.name")</tt>.

     *

     * @return the operating system name.

     *

     * @throws  java.lang.SecurityException

     *     if a security manager exists and its

     *     <code>checkPropertiesAccess</code> method doesn't allow access

     *     to this system property.

     * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)

     * @see java.lang.System#getProperty

     */

    public String getName();

    /**

     * Returns the operating system architecture.

     * This method is equivalent to <tt>System.getProperty("os.arch")</tt>.

     *

     * @return the operating system architecture.

     *

     * @throws  java.lang.SecurityException

     *     if a security manager exists and its

     *     <code>checkPropertiesAccess</code> method doesn't allow access

     *     to this system property.

     * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)

     * @see java.lang.System#getProperty

     */

    public String getArch();

    /**

     * Returns the operating system version.

     * This method is equivalent to <tt>System.getProperty("os.version")</tt>.

     *

     * @return the operating system version.

     *

     * @throws  java.lang.SecurityException

     *     if a security manager exists and its

     *     <code>checkPropertiesAccess</code> method doesn't allow access

     *     to this system property.

     * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)

     * @see java.lang.System#getProperty

     */

    public String getVersion();

    /**

     * Returns the number of processors available to the Java virtual machine.

     * This method is equivalent to the {@link Runtime#availableProcessors()}

     * method.

     * <p> This value may change during a particular invocation of

     * the virtual machine.

     *

     * @return  the number of processors available to the virtual

     *          machine; never smaller than one.

     */

    public int getAvailableProcessors();

    /**

     * Returns the system load average for the last minute.

     * The system load average is the sum of the number of runnable entities

     * queued to the {@linkplain #getAvailableProcessors available processors}

     * and the number of runnable entities running on the available processors

     * averaged over a period of time.

     * The way in which the load average is calculated is operating system

     * specific but is typically a damped time-dependent average.

     * <p>

     * If the load average is not available, a negative value is returned.

     * <p>

     * This method is designed to provide a hint about the system load

     * and may be queried frequently.

     * The load average may be unavailable on some platform where it is

     * expensive to implement this method.

     *

     * @return the system load average; or a negative value if not available.

     *

     * @since 1.6

     */

    public double getSystemLoadAverage();

}