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	/*
	* Copyright (c) 1998, 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.jdi;

	import java.util.List;
	import java.util.Map;

	/**
	* An object that currently exists in the target VM. An ObjectReference
	* mirrors only the object itself and is not specific to any
	* {@link Field} or {@link LocalVariable} to which it is currently
	* assigned. An ObjectReference can
	* have 0 or more references from field(s) and/or variable(s).
	* <p>
	* Any method on <code>ObjectReference</code> which directly or
	* indirectly takes <code>ObjectReference</code> as an parameter may throw
	* {@link com.sun.jdi.VMDisconnectedException} if the target VM is
	* disconnected and the {@link com.sun.jdi.event.VMDisconnectEvent} has been or is
	* available to be read from the {@link com.sun.jdi.event.EventQueue}.
	* <p>
	* Any method on <code>ObjectReference</code> which directly or
	* indirectly takes <code>ObjectReference</code> as an parameter may throw
	* {@link com.sun.jdi.VMOutOfMemoryException} if the target VM has run out of memory.
	* <p>
	* Any method on <code>ObjectReference</code> or which directly or indirectly takes
	* <code>ObjectReference</code> as parameter may throw
	* {@link com.sun.jdi.ObjectCollectedException} if the mirrored object has been
	* garbage collected.
	*
	* @author Robert Field
	* @author Gordon Hirsch
	* @author James McIlree
	* @since 1.3
	*/
	@jdk.Exported
	public interface ObjectReference extends Value {

	/**
	* Gets the {@link ReferenceType} that mirrors the type
	* of this object. The type may be a subclass or implementor of the
	* declared type of any field or variable which currently holds it.
	* For example, right after the following statement.
	* <p>
	* <code>Object obj = new String("Hello, world!");</code>
	* <p>
	* The ReferenceType of obj will mirror java.lang.String and not
	* java.lang.Object.
	* <p>
	* The type of an object never changes, so this method will
	* always return the same ReferenceType over the lifetime of the
	* mirrored object.
	* <p>
	* The returned ReferenceType will be a {@link ClassType} or
	* {@link ArrayType} and never an {@link InterfaceType}.
	*
	* @return the {@link ReferenceType} for this object.
	*/
	ReferenceType referenceType();

	/**
	* Gets the value of a given instance or static field in this object.
	* The Field must be valid for this ObjectReference;
	* that is, it must be from
	* the mirrored object's class or a superclass of that class.
	*
	* @param sig the field containing the requested value
	* @return the {@link Value} of the instance field.
	* @throws java.lang.IllegalArgumentException if the field is not valid for
	* this object's class.
	*/
	Value getValue(Field sig);

	/**
	* Gets the value of multiple instance and/or static fields in this object.
	* The Fields must be valid for this ObjectReference;
	* that is, they must be from
	* the mirrored object's class or a superclass of that class.
	*
	* @param fields a list of {@link Field} objects containing the
	* requested values.
	* @return a Map of the requested {@link Field} objects with
	* their {@link Value}.
	* @throws java.lang.IllegalArgumentException if any field is not valid for
	* this object's class.
	*/
	Map<Field,Value> getValues(List<? extends Field> fields);

	/**
	* Sets the value of a given instance or static field in this object.
	* The {@link Field} must be valid for this ObjectReference; that is,
	* it must be from the mirrored object's class or a superclass of that class.
	* If static, the field must not be final.
	* <p>
	* Object values must be assignment compatible with the field type
	* (This implies that the field type must be loaded through the
	* enclosing class's class loader). Primitive values must be
	* either assignment compatible with the field type or must be
	* convertible to the field type without loss of information.
	* See section 5.2 of
	* <cite>The Java™ Language Specification</cite>
	* for more information on assignment
	* compatibility.
	*
	* @param field the field containing the requested value
	* @param value the new value to assign
	* @throws java.lang.IllegalArgumentException if the field is not valid for
	* this object's class.
	* @throws InvalidTypeException if the value's type does not match
	* the field's type.
	* @throws ClassNotLoadedException if 'value' is not null, and the field
	* type has not yet been loaded through the appropriate class loader.
	* @throws VMCannotBeModifiedException if the VirtualMachine is read-only - see {@link VirtualMachine#canBeModified()}.
	*/
	void setValue(Field field, Value value)
	throws InvalidTypeException, ClassNotLoadedException;

	/** Perform method invocation with only the invoking thread resumed */
	static final int INVOKE_SINGLE_THREADED = 0x1;
	/** Perform non-virtual method invocation */
	static final int INVOKE_NONVIRTUAL = 0x2;

	/**
	* Invokes the specified {@link Method} on this object in the
	* target VM. The
	* specified method can be defined in this object's class,
	* in a superclass of this object's class, or in an interface
	* implemented by this object. The method may be a static method
	* or an instance method, but not a static initializer or constructor.
	* Use {@link ClassType#newInstance} to create a new object and
	* run its constructor.
	* <p>
	* The method invocation will occur in the specified thread.
	* Method invocation can occur only if the specified thread
	* has been suspended by an event which occurred in that thread.
	* Method invocation is not supported
	* when the target VM has been suspended through
	* {@link VirtualMachine#suspend} or when the specified thread
	* is suspended through {@link ThreadReference#suspend}.
	* <p>
	* The specified method is invoked with the arguments in the specified
	* argument list. The method invocation is synchronous; this method
	* does not return until the invoked method returns in the target VM.
	* If the invoked method throws an exception, this method
	* will throw an {@link InvocationException} which contains
	* a mirror to the exception object thrown.
	* <p>
	* Object arguments must be assignment compatible with the argument type
	* (This implies that the argument type must be loaded through the
	* enclosing class's class loader). Primitive arguments must be
	* either assignment compatible with the argument type or must be
	* convertible to the argument type without loss of information.
	* If the method being called accepts a variable number of arguments,
	* then the last argument type is an array of some component type.
	* The argument in the matching position can be omitted, or can be null,
	* an array of the same component type, or an argument of the
	* component type followed by any number of other arguments of the same
	* type. If the argument is omitted, then a 0 length array of the
	* component type is passed. The component type can be a primitive type.
	* Autoboxing is not supported.
	*
	* See section 5.2 of
	* <cite>The Java™ Language Specification</cite>
	* for more information on assignment compatibility.
	* <p>
	* By default, the method is invoked using dynamic lookup as
	* documented in section 15.12.4.4 of
	* <cite>The Java™ Language Specification</cite>
	* in particular, overriding based on the runtime type of the object
	* mirrored by this {@link ObjectReference} will occur. This
	* behavior can be changed by specifying the
	* {@link #INVOKE_NONVIRTUAL} bit flag in the <code>options</code>
	* argument. If this flag is set, the specified method is invoked
	* whether or not it is overridden for this object's runtime type.
	* The method, in this case, must have an implementation, either in a class
	* or an interface. This option is useful for performing method invocations
	* like those done with the <code>super</code> keyword in the Java programming
	* language.
	* <p>
	* By default, all threads in the target VM are resumed while
	* the method is being invoked if they were previously
	* suspended by an event or by {@link VirtualMachine#suspend} or
	* {@link ThreadReference#suspend}. This is done to prevent the deadlocks
	* that will occur if any of the threads own monitors
	* that will be needed by the invoked method.
	* Note, however, that this implicit resume acts exactly like
	* {@link ThreadReference#resume}, so if the thread's suspend
	* count is greater than 1, it will remain in a suspended state
	* during the invocation and thus a deadlock could still occur.
	* By default, when the invocation completes,
	* all threads in the target VM are suspended, regardless their state
	* before the invocation.
	* It is possible that
	* breakpoints or other events might occur during the invocation.
	* This can cause deadlocks as described above. It can also cause a deadlock
	* if invokeMethod is called from the client's event handler thread. In this
	* case, this thread will be waiting for the invokeMethod to complete and
	* won't read the EventSet that comes in for the new event. If this
	* new EventSet is SUSPEND_ALL, then a deadlock will occur because no
	* one will resume the EventSet. To avoid this, all EventRequests should
	* be disabled before doing the invokeMethod, or the invokeMethod should
	* not be done from the client's event handler thread.
	* <p>
	* The resumption of other threads during the invocation can be prevented
	* by specifying the {@link #INVOKE_SINGLE_THREADED}
	* bit flag in the <code>options</code> argument; however,
	* there is no protection against or recovery from the deadlocks
	* described above, so this option should be used with great caution.
	* Only the specified thread will be resumed (as described for all
	* threads above). Upon completion of a single threaded invoke, the invoking thread
	* will be suspended once again. Note that any threads started during
	* the single threaded invocation will not be suspended when the
	* invocation completes.
	* <p>
	* If the target VM is disconnected during the invoke (for example, through
	* {@link VirtualMachine#dispose}) the method invocation continues.
	*
	* @param thread the thread in which to invoke.
	* @param method the {@link Method} to invoke.
	* @param arguments the list of {@link Value} arguments bound to the
	* invoked method. Values from the list are assigned to arguments
	* in the order they appear in the method signature.
	* @param options the integer bit flag options.
	* @return a {@link Value} mirror of the invoked method's return value.
	* @throws java.lang.IllegalArgumentException if the method is not
	* a member of this object's class, if the size of the argument list
	* does not match the number of declared arguments for the method,
	* if the method is a constructor or static intializer, or
	* if {@link #INVOKE_NONVIRTUAL} is specified and the method is
	* either abstract or a non-default interface member.
	* @throws {@link InvalidTypeException} if any argument in the
	* argument list is not assignable to the corresponding method argument
	* type.
	* @throws ClassNotLoadedException if any argument type has not yet been loaded
	* through the appropriate class loader.
	* @throws IncompatibleThreadStateException if the specified thread has not
	* been suspended by an event.
	* @throws InvocationException if the method invocation resulted in
	* an exception in the target VM.
	* @throws InvalidTypeException If the arguments do not meet this requirement --
	* Object arguments must be assignment compatible with the argument
	* type. This implies that the argument type must be
	* loaded through the enclosing class's class loader.
	* Primitive arguments must be either assignment compatible with the
	* argument type or must be convertible to the argument type without loss
	* of information. See JLS section 5.2 for more information on assignment
	* compatibility.
	* @throws VMCannotBeModifiedException if the VirtualMachine is read-only - see {@link VirtualMachine#canBeModified()}.
	*/
	Value invokeMethod(ThreadReference thread, Method method,
	List<? extends Value> arguments, int options)
	throws InvalidTypeException,
	ClassNotLoadedException,
	IncompatibleThreadStateException,
	InvocationException;

	/**
	* Prevents garbage collection for this object. By default all
	* {@link ObjectReference} values returned by JDI may be collected
	* at any time the target VM is running. A call to this method
	* guarantees that the object will not be collected.
	* {@link #enableCollection} can be used to allow collection once
	* again.
	* <p>
	* Calls to this method are counted. Every call to this method
	* requires a corresponding call to {@link #enableCollection} before
	* garbage collection is re-enabled.
	* <p>
	* Note that while the target VM is suspended, no garbage collection
	* will occur because all threads are suspended. The typical
	* examination of variables, fields, and arrays during the suspension
	* is safe without explicitly disabling garbage collection.
	* <p>
	* This method should be used sparingly, as it alters the
	* pattern of garbage collection in the target VM and,
	* consequently, may result in application behavior under the
	* debugger that differs from its non-debugged behavior.
	* @throws VMCannotBeModifiedException if the VirtualMachine is read-only
	* -see {@link VirtualMachine#canBeModified()}.
	*/
	void disableCollection();

	/**
	* Permits garbage collection for this object. By default all
	* {@link ObjectReference} values returned by JDI may be collected
	* at any time the target VM is running. A call to this method
	* is necessary only if garbage collection was previously disabled
	* with {@link #disableCollection}.
	* @throws VMCannotBeModifiedException if the VirtualMachine is read-only
	* -see {@link VirtualMachine#canBeModified()}.
	*/
	void enableCollection();

	/**
	* Determines if this object has been garbage collected in the target
	* VM.
	*
	* @return <code>true</code> if this {@link ObjectReference} has been collected;
	* <code>false</code> otherwise.
	* @throws VMCannotBeModifiedException if the VirtualMachine is read-only
	* -see {@link VirtualMachine#canBeModified()}.
	*/
	boolean isCollected();

	/**
	* Returns a unique identifier for this ObjectReference.
	* It is guaranteed to be unique among all
	* ObjectReferences from the same VM that have not yet been disposed.
	* The guarantee applies as long
	* as this ObjectReference has not yet been disposed.
	*
	* @return a long unique ID
	*/
	long uniqueID();

	/**
	* Returns a List containing a {@link ThreadReference} for
	* each thread currently waiting for this object's monitor.
	* See {@link ThreadReference#currentContendedMonitor} for
	* information about when a thread is considered to be waiting
	* for a monitor.
	* <p>
	* Not all target VMs support this operation. See
	* VirtualMachine#canGetMonitorInfo to determine if the
	* operation is supported.
	*
	* @return a List of {@link ThreadReference} objects. The list
	* has zero length if no threads are waiting for the monitor.
	* @throws java.lang.UnsupportedOperationException if the
	* target VM does not support this operation.
	* @throws IncompatibleThreadStateException if any
	* waiting thread is not suspended
	* in the target VM
	*/
	List<ThreadReference> waitingThreads()
	throws IncompatibleThreadStateException;

	/**
	* Returns an {@link ThreadReference} for the thread, if any,
	* which currently owns this object's monitor.
	* See {@link ThreadReference#ownedMonitors} for a definition
	* of ownership.
	* <p>
	* Not all target VMs support this operation. See
	* VirtualMachine#canGetMonitorInfo to determine if the
	* operation is supported.
	*
	* @return the {@link ThreadReference} which currently owns the
	* monitor, or null if it is unowned.
	*
	* @throws java.lang.UnsupportedOperationException if the
	* target VM does not support this operation.
	* @throws IncompatibleThreadStateException if the owning thread is
	* not suspended in the target VM
	*/
	ThreadReference owningThread() throws IncompatibleThreadStateException;

	/**
	* Returns the number times this object's monitor has been
	* entered by the current owning thread.
	* See {@link ThreadReference#ownedMonitors} for a definition
	* of ownership.
	* <p>
	* Not all target VMs support this operation. See
	* VirtualMachine#canGetMonitorInfo to determine if the
	* operation is supported.
	*
	* @see #owningThread
	* @return the integer count of the number of entries.
	*
	* @throws java.lang.UnsupportedOperationException if the
	* target VM does not support this operation.
	* @throws IncompatibleThreadStateException if the owning thread is
	* not suspended in the target VM
	*/
	int entryCount() throws IncompatibleThreadStateException;

	/**
	* Returns objects that directly reference this object.
	* Only objects that are reachable for the purposes of garbage collection
	* are returned. Note that an object can also be referenced in other ways,
	* such as from a local variable in a stack frame, or from a JNI global
	* reference. Such non-object referrers are not returned by this method.
	* <p>
	* Not all target virtual machines support this operation.
	* Use {@link VirtualMachine#canGetInstanceInfo()}
	* to determine if the operation is supported.
	*
	* @see VirtualMachine#instanceCounts(List)
	* @see ReferenceType#instances(long)

	* @param maxReferrers The maximum number of referring objects to return.
	* Must be non-negative. If zero, all referring
	* objects are returned.
	* @return a of List of {@link ObjectReference} objects. If there are
	* no objects that reference this object, a zero-length list is returned..
	* @throws java.lang.UnsupportedOperationException if
	* the target virtual machine does not support this
	* operation - see
	* {@link VirtualMachine#canGetInstanceInfo() canGetInstanceInfo()}
	* @throws java.lang.IllegalArgumentException if maxReferrers is less
	* than zero.
	* @since 1.6
	*/
	List<ObjectReference> referringObjects(long maxReferrers);


	/**
	* Compares the specified Object with this ObjectReference for equality.
	*
	* @return true if the Object is an ObjectReference, if the
	* ObjectReferences belong to the same VM, and if applying the
	* "==" operator on the mirrored objects in that VM evaluates to true.
	*/
	boolean equals(Object obj);

	/**
	* Returns the hash code value for this ObjectReference.
	*
	* @return the integer hash code
	*/
	int hashCode();
	}

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