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	/*
	* Copyright (c) 2005, 2013, 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.tools.attach;

	import com.sun.tools.attach.spi.AttachProvider;

	/**
	* Describes a Java virtual machine.
	*
	* <p> A <code>VirtualMachineDescriptor</code> is a container class used to
	* describe a Java virtual machine. It encapsulates an identifier that identifies
	* a target virtual machine, and a reference to the {@link
	* com.sun.tools.attach.spi.AttachProvider AttachProvider} that should be used
	* when attempting to attach to the virtual machine. The identifier is
	* implementation-dependent but is typically the process identifier (or pid)
	* environments where each Java virtual machine runs in its own operating system
	* process. </p>
	*
	* <p> A <code>VirtualMachineDescriptor</code> also has a {@link #displayName() displayName}.
	* The display name is typically a human readable string that a tool might
	* display to a user. For example, a tool that shows a list of Java
	* virtual machines running on a system might use the display name rather
	* than the identifier. A <code>VirtualMachineDescriptor</code> may be
	* created without a <i>display name</i>. In that case the identifier is
	* used as the <i>display name</i>.
	*
	* <p> <code>VirtualMachineDescriptor</code> instances are typically created by
	* invoking the {@link com.sun.tools.attach.VirtualMachine#list VirtualMachine.list()}
	* method. This returns the complete list of descriptors to describe the
	* Java virtual machines known to all installed {@link
	* com.sun.tools.attach.spi.AttachProvider attach providers}.
	*
	* @since 1.6
	*/
	@jdk.Exported
	public class VirtualMachineDescriptor {

	private AttachProvider provider;
	private String id;
	private String displayName;

	private volatile int hash; // 0 => not computed

	/**
	* Creates a virtual machine descriptor from the given components.
	*
	* @param provider The AttachProvider to attach to the Java virtual machine.
	* @param id The virtual machine identifier.
	* @param displayName The display name.
	*
	* @throws NullPointerException
	* If any of the arguments are <code>null</code>
	*/
	public VirtualMachineDescriptor(AttachProvider provider, String id, String displayName) {
	if (provider == null) {
	throw new NullPointerException("provider cannot be null");
	}
	if (id == null) {
	throw new NullPointerException("identifier cannot be null");
	}
	if (displayName == null) {
	throw new NullPointerException("display name cannot be null");
	}
	this.provider = provider;
	this.id = id;
	this.displayName = displayName;
	}

	/**
	* Creates a virtual machine descriptor from the given components.
	*
	* <p> This convenience constructor works as if by invoking the
	* three-argument constructor as follows:
	*
	* <blockquote><tt>
	* new {@link #VirtualMachineDescriptor(AttachProvider, String, String)
	* VirtualMachineDescriptor}(provider,  id,  id);
	* </tt></blockquote>
	*
	* <p> That is, it creates a virtual machine descriptor such that
	* the <i>display name</i> is the same as the virtual machine
	* identifier.
	*
	* @param provider The AttachProvider to attach to the Java virtual machine.
	* @param id The virtual machine identifier.
	*
	* @throws NullPointerException
	* If <tt>provider</tt> or <tt>id</tt> is <tt>null</tt>.
	*/
	public VirtualMachineDescriptor(AttachProvider provider, String id) {
	this(provider, id, id);
	}

	/**
	* Return the <code>AttachProvider</code> that this descriptor references.
	*
	* @return The <code>AttachProvider</code> that this descriptor references.
	*/
	public AttachProvider provider() {
	return provider;
	}

	/**
	* Return the identifier component of this descriptor.
	*
	* @return The identifier component of this descriptor.
	*/
	public String id() {
	return id;
	}

	/**
	* Return the <i>display name</i> component of this descriptor.
	*
	* @return The display name component of this descriptor.
	*/
	public String displayName() {
	return displayName;
	}

	/**
	* Returns a hash-code value for this VirtualMachineDescriptor. The hash
	* code is based upon the descriptor's components, and satifies
	* the general contract of the {@link java.lang.Object#hashCode()
	* Object.hashCode} method.
	*
	* @return A hash-code value for this descriptor.
	*/
	public int hashCode() {
	if (hash != 0) {
	return hash;
	}
	hash = provider.hashCode() * 127 + id.hashCode();
	return hash;
	}

	/**
	* Tests this VirtualMachineDescriptor for equality with another object.
	*
	* <p> If the given object is not a VirtualMachineDescriptor then this
	* method returns <tt>false</tt>. For two VirtualMachineDescriptors to
	* be considered equal requires that they both reference the same
	* provider, and their {@link #id() identifiers} are equal. </p>
	*
	* <p> This method satisfies the general contract of the {@link
	* java.lang.Object#equals(Object) Object.equals} method. </p>
	*
	* @param ob The object to which this object is to be compared
	*
	* @return <tt>true</tt> if, and only if, the given object is
	* a VirtualMachineDescriptor that is equal to this
	* VirtualMachineDescriptor.
	*/
	public boolean equals(Object ob) {
	if (ob == this)
	return true;
	if (!(ob instanceof VirtualMachineDescriptor))
	return false;
	VirtualMachineDescriptor other = (VirtualMachineDescriptor)ob;
	if (other.provider() != this.provider()) {
	return false;
	}
	if (!other.id().equals(this.id())) {
	return false;
	}
	return true;
	}

	/**
	* Returns the string representation of the <code>VirtualMachineDescriptor</code>.
	*/
	public String toString() {
	String s = provider.toString() + ": " + id;
	if (displayName != id) {
	s += " " + displayName;
	}
	return s;
	}


	}

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