https://openjdk.java.net/ 
/*
 * Copyright (c) 2005, 2006, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 com.sun.management;

import sun.management.VMOptionCompositeData;
import javax.management.openmbean.CompositeData;


Information about a VM option including its value and where the value came from which is referred as its origin. 

Each VM option has a default value.  A VM option can
be set at VM creation time typically as a command line
argument to the launcher or an argument passed to the
VM created using the JNI invocation interface.
In addition, a VM option may be set via an environment
variable or a configuration file. A VM option can also
be set dynamically via a management interface after
the VM was started.
A VMOption contains the value of a VM option
and the origin of that value at the time this VMOption
object was constructed.  The value of the VM option
may be changed after the VMOption object was constructed,

Author:Mandy Chung
See Also:
Since:1.6
/**
 * Information about a VM option including its value and
 * where the value came from which is referred as its
 * {@link VMOption.Origin <i>origin</i>}.
 * <p>
 * Each VM option has a default value.  A VM option can
 * be set at VM creation time typically as a command line
 * argument to the launcher or an argument passed to the
 * VM created using the JNI invocation interface.
 * In addition, a VM option may be set via an environment
 * variable or a configuration file. A VM option can also
 * be set dynamically via a management interface after
 * the VM was started.
 *
 * A <tt>VMOption</tt> contains the value of a VM option
 * and the origin of that value at the time this <tt>VMOption</tt>
 * object was constructed.  The value of the VM option
 * may be changed after the <tt>VMOption</tt> object was constructed,
 *
 * @see <a href="{@docRoot}/../../../../technotes/guides/vm/index.html">
 *         Java Virtual Machine</a>
 * @author Mandy Chung
 * @since 1.6
 */
public class VMOption {
    private String name;
    private String value;
    private boolean writeable;
    private Origin origin;

    
Origin of the value of a VM option.  It tells where the
value of a VM option came from.

Since:1.6
/**
     * Origin of the value of a VM option.  It tells where the
     * value of a VM option came from.
     *
     * @since 1.6
     */
    public enum Origin {
        
The VM option has not been set and its value
is the default value.

/**
         * The VM option has not been set and its value
         * is the default value.
         */
        DEFAULT,
        
The VM option was set at VM creation time typically
as a command line argument to the launcher or
an argument passed to the VM created using the
JNI invocation interface.

/**
         * The VM option was set at VM creation time typically
         * as a command line argument to the launcher or
         * an argument passed to the VM created using the
         * JNI invocation interface.
         */
        VM_CREATION,
        
The VM option was set via an environment variable.

/**
         * The VM option was set via an environment variable.
         */
        ENVIRON_VAR,
        
The VM option was set via a configuration file.

/**
         * The VM option was set via a configuration file.
         */
        CONFIG_FILE,
        
The VM option was set via the management interface after the VM
was started.

/**
         * The VM option was set via the management interface after the VM
         * was started.
         */
        MANAGEMENT,
        
The VM option was set via the VM ergonomic support.

/**
         * The VM option was set via the VM ergonomic support.
         */
        ERGONOMIC,
        
The VM option was set via some other mechanism.

/**
         * The VM option was set via some other mechanism.
         */
        OTHER
    }

    
Constructs a VMOption.

Params:
  • name – Name of a VM option.
  • value – Value of a VM option.
  • writeable – true if a VM option can be set dynamically,
                 or false otherwise.
  • origin – where the value of a VM option came from.
Throws:
/**
     * Constructs a <tt>VMOption</tt>.
     *
     * @param name Name of a VM option.
     * @param value Value of a VM option.
     * @param writeable <tt>true</tt> if a VM option can be set dynamically,
     *                  or <tt>false</tt> otherwise.
     * @param origin where the value of a VM option came from.
     *
     * @throws NullPointerException if the name or value is <tt>null</tt>
     */
    public VMOption(String name, String value, boolean writeable, Origin origin) {
        this.name = name;
        this.value = value;
        this.writeable = writeable;
        this.origin = origin;
    }

    
Constructs a VMOption object from a CompositeData. 
/**
     * Constructs a <tt>VMOption</tt> object from a
     * {@link CompositeData CompositeData}.
     */
    private VMOption(CompositeData cd) {
        // validate the input composite data
        VMOptionCompositeData.validateCompositeData(cd);

        this.name = VMOptionCompositeData.getName(cd);
        this.value = VMOptionCompositeData.getValue(cd);
        this.writeable = VMOptionCompositeData.isWriteable(cd);
        this.origin = VMOptionCompositeData.getOrigin(cd);
    }

    
Returns the name of this VM option.

Returns:the name of this VM option.
/**
     * Returns the name of this VM option.
     *
     * @return the name of this VM option.
     */
    public String getName() {
        return name;
    }

    
Returns the value of this VM option at the time when
this VMOption was created. The value could have been changed.

Returns:the value of the VM option at the time when
        this VMOption was created.
/**
     * Returns the value of this VM option at the time when
     * this <tt>VMOption</tt> was created. The value could have been changed.
     *
     * @return the value of the VM option at the time when
     *         this <tt>VMOption</tt> was created.
     */
    public String getValue() {
        return value;
    }

    
Returns the origin of the value of this VM option. That is,
where the value of this VM option came from.

Returns:where the value of this VM option came from.
/**
     * Returns the origin of the value of this VM option. That is,
     * where the value of this VM option came from.
     *
     * @return where the value of this VM option came from.
     */
    public Origin getOrigin() {
        return origin;
    }

    
Tests if this VM option is writeable. If this VM option is writeable, it can be set by the 
HotSpotDiagnosticMXBean.setVMOption method. 
Returns:true if this VM option is writeable; false
otherwise.
/**
     * Tests if this VM option is writeable.  If this VM option is writeable,
     * it can be set by the {@link HotSpotDiagnosticMXBean#setVMOption
     * HotSpotDiagnosticMXBean.setVMOption} method.
     *
     * @return <tt>true</tt> if this VM option is writeable; <tt>false</tt>
     * otherwise.
     */
    public boolean isWriteable() {
        return writeable;
    }

    public String toString() {
        return "VM option: " + getName() +
               " value: " + value + " " +
               " origin: " + origin + " " +
               (writeable ? "(read-only)" : "(read-write)");
    }

    
Returns a VMOption object represented by the
given CompositeData. The given CompositeData
must contain the following attributes:








  Attribute Name
  Type




  name
  java.lang.String




  value
  java.lang.String




  origin
  java.lang.String




  writeable
  java.lang.Boolean







Params:
  • cd – CompositeData representing a VMOption
Throws:
Returns:a VMOption object represented by cd
        if cd is not null;
        null otherwise.
/**
     * Returns a <tt>VMOption</tt> object represented by the
     * given <tt>CompositeData</tt>. The given <tt>CompositeData</tt>
     * must contain the following attributes:
     * <p>
     * <blockquote>
     * <table border>
     * <tr>
     *   <th align=left>Attribute Name</th>
     *   <th align=left>Type</th>
     * </tr>
     * <tr>
     *   <td>name</td>
     *   <td><tt>java.lang.String</tt></td>
     * </tr>
     * <tr>
     *   <td>value</td>
     *   <td><tt>java.lang.String</tt></td>
     * </tr>
     * <tr>
     *   <td>origin</td>
     *   <td><tt>java.lang.String</tt></td>
     * </tr>
     * <tr>
     *   <td>writeable</td>
     *   <td><tt>java.lang.Boolean</tt></td>
     * </tr>
     * </table>
     * </blockquote>
     *
     * @param cd <tt>CompositeData</tt> representing a <tt>VMOption</tt>
     *
     * @throws IllegalArgumentException if <tt>cd</tt> does not
     *   represent a <tt>VMOption</tt> with the attributes described
     *   above.
     *
     * @return a <tt>VMOption</tt> object represented by <tt>cd</tt>
     *         if <tt>cd</tt> is not <tt>null</tt>;
     *         <tt>null</tt> otherwise.
     */
    public static VMOption from(CompositeData cd) {
        if (cd == null) {
            return null;
        }

        if (cd instanceof VMOptionCompositeData) {
            return ((VMOptionCompositeData) cd).getVMOption();
        } else {
            return new VMOption(cd);
        }

    }


}