# Interface VirtualMachine

All Superinterfaces:
  `Mirror`

All Known Subinterfaces:
  `PathSearchingVirtualMachine`

public interface VirtualMachine extends Mirror
A virtual machine targeted for debugging. More precisely, a `mirror` representing the composite state of the target VM. All other mirrors are associated with an instance of this interface. Access to all other mirrors is achieved directly or indirectly through an instance of this interface. Access to global VM properties and control of VM execution are supported directly by this interface.

Instances of this interface are created by instances of `Connector`. For example, an `AttachingConnector` attaches to a target VM and returns its virtual machine mirror. A Connector will typically create a VirtualMachine by invoking the VirtualMachineManager's `VirtualMachineManager.createVirtualMachine(Connection)` createVirtualMachine(Connection) method.

Note that a target VM launched by a launching connector is not guaranteed to be stable until after the `VMStartEvent` has been received.

Any method on `VirtualMachine` which takes `VirtualMachine` as an parameter may throw `VMDisconnectedException` if the target VM is disconnected and the `VMDisconnectEvent` has been or is available to be read from the `EventQueue`.

Any method on `VirtualMachine` which takes `VirtualMachine` as an parameter may throw `VMOutOfMemoryException` if the target VM has run out of memory.

Since:
  1.3

## Field Summary

Fields
Modifier and Type
Field
Description
`static final int`
`TRACE_ALL`
All tracing is enabled.
`static final int`
`TRACE_EVENTS`
Tracing enabled for internal event handling.
`static final int`
`TRACE_NONE`
All tracing is disabled.
`static final int`
`TRACE_OBJREFS`
Tracing enabled for internal management of object references.
`static final int`
`TRACE_RECEIVES`
Tracing enabled for JDWP packets received from target VM.
`static final int`
`TRACE_REFTYPES`
Tracing enabled for internal management of reference types.
`static final int`
`TRACE_SENDS`
Tracing enabled for JDWP packets sent to target VM.

## Method Summary

Modifier and Type
Method
Description
`List<ReferenceType>`
`allClasses()`
Returns all loaded types in the target VM.
`default List<ModuleReference>`
`allModules()`
Returns all modules.
`List<ThreadReference>`
`allThreads()`
Returns a list of the live threads in the target VM.
`boolean`
`canAddMethod()`
Deprecated.
A JVM TI based JDWP back-end will never set this capability to true.
`boolean`
`canBeModified()`
Determines if the target VM is a read-only VM.
`boolean`
`canForceEarlyReturn()`
Determines if the target VM supports the forcing of a method to return early.
`boolean`
`canGetBytecodes()`
Determines if the target VM supports the retrieval of a method's bytecodes.
`boolean`
`canGetClassFileVersion()`
Determines if the target VM supports reading class file major and minor versions.
`boolean`
`canGetConstantPool()`
Determines if the target VM supports getting constant pool information of a class.
`boolean`
`canGetCurrentContendedMonitor()`
Determines if the target VM supports the retrieval of the monitor for which a thread is currently waiting.
`boolean`
`canGetInstanceInfo()`
Determines if the target VM supports the accessing of class instances, instance counts, and referring objects.
`boolean`
`canGetMethodReturnValues()`
Determines if the target VM supports the inclusion of return values in `MethodExitEvent`s.
`default boolean`
`canGetModuleInfo()`
Determines if the target VM supports getting information about modules.
`boolean`
`canGetMonitorFrameInfo()`
Determines if the target VM supports getting which frame has acquired a monitor.
`boolean`
`canGetMonitorInfo()`
Determines if the target VM supports the retrieval of the monitor information for an object.
`boolean`
`canGetOwnedMonitorInfo()`
Determines if the target VM supports the retrieval of the monitors owned by a thread.
`boolean`
`canGetSourceDebugExtension()`
Determines if the target VM supports getting the source debug extension.
`boolean`
`canGetSyntheticAttribute()`
Determines if the target VM supports the query of the synthetic attribute of a method or field.
`boolean`
`canPopFrames()`
Determines if the target VM supports popping frames of a threads stack.
`boolean`
`canRedefineClasses()`
Determines if the target VM supports any level of class redefinition.
`boolean`
`canRequestMonitorEvents()`
Determines if the target VM supports the creation of `MonitorContendedEnterRequest`s.
`boolean`
`canRequestVMDeathEvent()`
Determines if the target VM supports the creation of `VMDeathRequest`s.
`boolean`
`canUnrestrictedlyRedefineClasses()`
Deprecated.
A JVM TI based JDWP back-end will never set this capability to true.
`boolean`
`canUseInstanceFilters()`
Determines if the target VM supports filtering events by specific instance object.
`boolean`
`canUseSourceNameFilters()`
Determines if the target VM supports the filtering of class prepare events by source name.
`boolean`
`canWatchFieldAccess()`
Determines if the target VM supports watchpoints for field access.
`boolean`
`canWatchFieldModification()`
Determines if the target VM supports watchpoints for field modification.
`List<ReferenceType>`
`classesByName(String className)`
Returns the loaded reference types that match a given name.
`String`
`description()`
Returns text information on the target VM and the debugger support that mirrors it.
`void`
`dispose()`
Invalidates this virtual machine mirror.
`EventQueue`
`eventQueue()`
Returns the event queue for this virtual machine.
`EventRequestManager`
`eventRequestManager()`
Returns the event request manager for this virtual machine.
`void`
`exit(int exitCode)`
Causes the mirrored VM to terminate with the given error code.
`String`
`getDefaultStratum()`
Return this VM's default stratum.
`long[]`
`instanceCounts(List<? extends ReferenceType> refTypes)`
Returns the number of instances of each ReferenceType in the 'refTypes' list.
`BooleanValue`
`mirrorOf(boolean value)`
Creates a `BooleanValue` for the given value.
`ByteValue`
`mirrorOf(byte value)`
Creates a `ByteValue` for the given value.
`CharValue`
`mirrorOf(char value)`
Creates a `CharValue` for the given value.
`DoubleValue`
`mirrorOf(double value)`
Creates a `DoubleValue` for the given value.
`FloatValue`
`mirrorOf(float value)`
Creates a `FloatValue` for the given value.
`IntegerValue`
`mirrorOf(int value)`
Creates an `IntegerValue` for the given value.
`LongValue`
`mirrorOf(long value)`
Creates a `LongValue` for the given value.
`ShortValue`
`mirrorOf(short value)`
Creates a `ShortValue` for the given value.
`StringReference`
`mirrorOf(String value)`
Creates a string in this virtual machine.
`VoidValue`
`mirrorOfVoid()`
Creates a `VoidValue`.
`String`
`name()`
Returns the name of the target VM as reported by the property `java.vm.name`.
`Process`
`process()`
Returns the `Process` object for this virtual machine if launched by a `LaunchingConnector`
`void`
`redefineClasses(Map<? extends ReferenceType, byte[]> classToBytes)`
All classes given are redefined according to the definitions supplied.
`void`
`resume()`
Continues the execution of the application running in this virtual machine.
`void`
`setDebugTraceMode(int traceFlags)`
Traces the activities performed by the com.sun.jdi implementation.
`void`
`setDefaultStratum(String stratum)`
Set this VM's default stratum (see `Location` for a discussion of strata).
`void`
`suspend()`
Suspends the execution of the application running in this virtual machine.
`List<ThreadGroupReference>`
`topLevelThreadGroups()`
Returns each thread group which does not have a parent.
`String`
`version()`
Returns the version of the Java Runtime Environment in the target VM as reported by the property `java.version`.

### Methods declared in interface Mirror

`toString, virtualMachine`

## Field Details

### TRACE_NONE

static final int TRACE_NONE
All tracing is disabled.

See Also:
  - Constant Field Values

### TRACE_SENDS

static final int TRACE_SENDS
Tracing enabled for JDWP packets sent to target VM.

See Also:
  - Constant Field Values

### TRACE_RECEIVES

static final int TRACE_RECEIVES
Tracing enabled for JDWP packets received from target VM.

See Also:
  - Constant Field Values

### TRACE_EVENTS

static final int TRACE_EVENTS
Tracing enabled for internal event handling.

See Also:
  - Constant Field Values

### TRACE_REFTYPES

static final int TRACE_REFTYPES
Tracing enabled for internal management of reference types.

See Also:
  - Constant Field Values

### TRACE_OBJREFS

static final int TRACE_OBJREFS
Tracing enabled for internal management of object references.

See Also:
  - Constant Field Values

### TRACE_ALL

static final int TRACE_ALL
All tracing is enabled.

See Also:
  - Constant Field Values

## Method Details

### allModules

default List<ModuleReference> allModules()
Returns all modules. For each module in the target VM a `ModuleReference` will be placed in the returned list.

Not all target virtual machines support this operation. Use `canGetModuleInfo()` to determine if the operation is supported.

Implementation Requirements:
  The default implementation throws `UnsupportedOperationException`.
Returns:
  a list of `ModuleReference` objects, each mirroring a module in the target VM.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation.
Since:
  9

### classesByName

List<ReferenceType> classesByName(String className)
Returns the loaded reference types that match a given name. The name must be fully qualified (for example, java.lang.String). The returned list will contain a `ReferenceType` for each class or interface found with the given name. The search is confined to loaded classes only; no attempt is made to load a class of the given name.

The returned list will include reference types loaded at least to the point of preparation and types (like array) for which preparation is not defined.

Parameters:
  `className` - the class/interface name to search for
Returns:
  a list of `ReferenceType` objects, each mirroring a type in the target VM with the given name.

### allClasses

List<ReferenceType> allClasses()
Returns all loaded types in the target VM.

The returned list includes all reference types, including `hidden classes or interfaces`, loaded at least to the point of preparation and types (like array) for which preparation is not defined.

Returns:
  a list of `ReferenceType` objects, each mirroring a loaded type in the target VM.
See Also:
  - JVM TI GetLoadedClasses regarding how class and interface creation can be triggered

### redefineClasses

void redefineClasses(Map<? extends ReferenceType, byte[]> classToBytes)
All classes given are redefined according to the definitions supplied. A method in a redefined class is called 'equivalent' (to the old version of the method) if

- their bytecodes are the same except for indices into the constant pool, and
- the referenced constants are equal.

Otherwise, the new method is called 'non-equivalent'. If a redefined method has active stack frames, those active frames continue to run the bytecodes of the previous version of the method. If the new version of such a method is non-equivalent, then a method from one of these active frames is called 'obsolete' and `Method.isObsolete()` will return true when called on one of these methods. If resetting such a frame is desired, use `ThreadReference.popFrames(StackFrame)` to pop the old obsolete method execution from the stack. New invocations of redefined methods will always invoke the new versions.

This function does not cause any initialization except that which would occur under the customary JVM semantics. In other words, redefining a class does not cause its initializers to be run. The values of preexisting static variables will remain as they were prior to the call. However, completely uninitialized (new) static variables will be assigned their default value.

If a redefined class has instances then all those instances will have the fields defined by the redefined class at the completion of the call. Preexisting fields will retain their previous values. Any new fields will have their default values; no instance initializers or constructors are run.

Threads need not be suspended.

No events are generated by this function.

All breakpoints in the redefined classes are deleted.

Not all target virtual machines support this operation. Use `canRedefineClasses()` to determine if the operation is supported. Use `canAddMethod()` to determine if the redefinition can add methods. Use `canUnrestrictedlyRedefineClasses()` to determine if the redefinition can change the schema, delete methods, change the class hierarchy, etc.

Parameters:
  `classToBytes` - A map from `ReferenceType` to array of byte. The bytes represent the new class definition and are in Java Virtual Machine class file format.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation.
  - If `canRedefineClasses()` is false any call of this method will throw this exception.
  - If `canAddMethod()` is false attempting to add a method will throw this exception.
  - If `canUnrestrictedlyRedefineClasses()` is false attempting any of the unsupported class file changes described in JVM TI RedefineClasses will throw this exception.
  `NoClassDefFoundError` - if the bytes don't correspond to the reference type (the names don't match).
  `VerifyError` - if a "verifier" detects that a class, though well formed, contains an internal inconsistency or security problem.
  `ClassFormatError` - if the bytes do not represent a valid class.
  `ClassCircularityError` - if a circularity has been detected while initializing a class.
  `UnsupportedClassVersionError` - if the major and minor version numbers in bytes are not supported by the VM.
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.
Since:
  1.4
See Also:
  - `Method.isObsolete()`
  - `ThreadReference.popFrames(StackFrame)`
  - `canRedefineClasses()`
  - `canAddMethod()`
  - `canUnrestrictedlyRedefineClasses()`

### allThreads

List<ThreadReference> allThreads()
Returns a list of the live threads in the target VM. Threads that have not yet started or threads that have terminated are not included in the list.

The returned list contains a `ThreadReference` for each live platform thread in the target VM. This includes platform threads created with the `java.lang.Thread` API and all native threads attached to the target VM with JNI code.

It is implementation dependent if the list contains elements for live virtual threads in the target VM. The target VM may not return any references to virtual threads, or it may be configured to return a reference to some or all virtual threads. Tools that want to track all virtual threads may enable `ThreadStartRequest` and `ThreadDeathRequest` to get notifications when virtual threads start and terminate.

Returns:
  a list of `ThreadReference` objects for the threads in the target VM

### suspend

void suspend()
Suspends the execution of the application running in this virtual machine. All threads currently running will be suspended.

Suspends of both the virtual machine and individual threads are counted. Before a thread will run again, it must be resumed (through `resume()` or `ThreadReference.resume()`) the same number of times it has been suspended.

Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only
See Also:
  - `canBeModified()`

### resume

void resume()
Continues the execution of the application running in this virtual machine. All threads are resumed as documented in `ThreadReference.resume()`.

Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only
See Also:
  - `suspend()`
  - `canBeModified()`

### topLevelThreadGroups

List<ThreadGroupReference> topLevelThreadGroups()
Returns each thread group which does not have a parent. For each top level thread group a `ThreadGroupReference` is placed in the returned list.

This command may be used as the first step in building a tree (or trees) of the existing thread groups.

Returns:
  a list of `ThreadGroupReference` objects, one for each top level thread group.

### eventQueue

EventQueue eventQueue()
Returns the event queue for this virtual machine. A virtual machine has only one `EventQueue` object, this method will return the same instance each time it is invoked.

Returns:
  the `EventQueue` for this virtual machine.
Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.

### eventRequestManager

EventRequestManager eventRequestManager()
Returns the event request manager for this virtual machine. The `EventRequestManager` controls user settable events such as breakpoints. A virtual machine has only one `EventRequestManager` object, this method will return the same instance each time it is invoked.

Returns:
  the `EventRequestManager` for this virtual machine.
Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.

### mirrorOf

BooleanValue mirrorOf(boolean value)
Creates a `BooleanValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a boolean for which to create the value
Returns:
  the `BooleanValue` for the given boolean.

### mirrorOf

ByteValue mirrorOf(byte value)
Creates a `ByteValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a byte for which to create the value
Returns:
  the `ByteValue` for the given byte.

### mirrorOf

CharValue mirrorOf(char value)
Creates a `CharValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a char for which to create the value
Returns:
  the `CharValue` for the given char.

### mirrorOf

ShortValue mirrorOf(short value)
Creates a `ShortValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a short for which to create the value
Returns:
  the `ShortValue` for the given short.

### mirrorOf

IntegerValue mirrorOf(int value)
Creates an `IntegerValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - an int for which to create the value
Returns:
  the `IntegerValue` for the given int.

### mirrorOf

LongValue mirrorOf(long value)
Creates a `LongValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a long for which to create the value
Returns:
  the `LongValue` for the given long.

### mirrorOf

FloatValue mirrorOf(float value)
Creates a `FloatValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a float for which to create the value
Returns:
  the `FloatValue` for the given float.

### mirrorOf

DoubleValue mirrorOf(double value)
Creates a `DoubleValue` for the given value. This value can be used for setting and comparing against a value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - a double for which to create the value
Returns:
  the `DoubleValue` for the given double.

### mirrorOf

StringReference mirrorOf(String value)
Creates a string in this virtual machine. The created string can be used for setting and comparing against a string value retrieved from a variable or field in this virtual machine.

Parameters:
  `value` - the string to be created
Returns:
  a `StringReference` that mirrors the newly created string in the target VM.
Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.

### mirrorOfVoid

VoidValue mirrorOfVoid()
Creates a `VoidValue`. This value can be passed to `ThreadReference.forceEarlyReturn(Value)` when a void method is to be exited.

Returns:
  the `VoidValue`.

### process

Process process()
Returns the `Process` object for this virtual machine if launched by a `LaunchingConnector`

Returns:
  the `Process` object for this virtual machine, or null if it was not launched by a `LaunchingConnector`.
Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.

### dispose

void dispose()
Invalidates this virtual machine mirror. The communication channel to the target VM is closed, and the target VM prepares to accept another subsequent connection from this debugger or another debugger, including the following tasks:

- All event requests are cancelled.
- All threads suspended by `suspend()` or by `ThreadReference.suspend()` are resumed as many times as necessary for them to run.
- Garbage collection is re-enabled in all cases where it was disabled through `ObjectReference.disableCollection()`.

Any current method invocations executing in the target VM are continued after the disconnection. Upon completion of any such method invocation, the invoking thread continues from the location where it was originally stopped.

Resources originating in this VirtualMachine (ObjectReferences, ReferenceTypes, etc.) will become invalid.

### exit

void exit(int exitCode)
Causes the mirrored VM to terminate with the given error code. All resources associated with this VirtualMachine are freed. If the mirrored VM is remote, the communication channel to it will be closed. Resources originating in this VirtualMachine (ObjectReferences, ReferenceTypes, etc.) will become invalid.

Threads running in the mirrored VM are abruptly terminated. A thread death exception is not thrown and finally blocks are not run.

Parameters:
  `exitCode` - the exit code for the target VM. On some platforms, the exit code might be truncated, for example, to the lower order 8 bits.
Throws:
  `VMCannotBeModifiedException` - if the VirtualMachine is read-only - see `canBeModified()`.

### canWatchFieldModification

boolean canWatchFieldModification()
Determines if the target VM supports watchpoints for field modification.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canWatchFieldAccess

boolean canWatchFieldAccess()
Determines if the target VM supports watchpoints for field access.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canGetBytecodes

boolean canGetBytecodes()
Determines if the target VM supports the retrieval of a method's bytecodes.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canGetSyntheticAttribute

boolean canGetSyntheticAttribute()
Determines if the target VM supports the query of the synthetic attribute of a method or field.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canGetOwnedMonitorInfo

boolean canGetOwnedMonitorInfo()
Determines if the target VM supports the retrieval of the monitors owned by a thread.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canGetCurrentContendedMonitor

boolean canGetCurrentContendedMonitor()
Determines if the target VM supports the retrieval of the monitor for which a thread is currently waiting.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canGetMonitorInfo

boolean canGetMonitorInfo()
Determines if the target VM supports the retrieval of the monitor information for an object.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canUseInstanceFilters

boolean canUseInstanceFilters()
Determines if the target VM supports filtering events by specific instance object. For example, see `BreakpointRequest.addInstanceFilter(ObjectReference)`.

Returns:
  `true` if the feature is supported, `false` otherwise.

### canRedefineClasses

boolean canRedefineClasses()
Determines if the target VM supports any level of class redefinition.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `redefineClasses(Map)`

### canAddMethod

@Deprecated(since="15") boolean canAddMethod()
Deprecated.
A JVM TI based JDWP back-end will never set this capability to true.
Determines if the target VM supports the addition of methods when performing class redefinition.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `redefineClasses(Map)`

### canUnrestrictedlyRedefineClasses

@Deprecated(since="15") boolean canUnrestrictedlyRedefineClasses()
Deprecated.
A JVM TI based JDWP back-end will never set this capability to true.
Determines if the target VM supports changes when performing class redefinition that are otherwise restricted by `redefineClasses(Map)`.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `redefineClasses(Map)`

### canPopFrames

boolean canPopFrames()
Determines if the target VM supports popping frames of a threads stack.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `ThreadReference.popFrames(StackFrame)`

### canGetSourceDebugExtension

boolean canGetSourceDebugExtension()
Determines if the target VM supports getting the source debug extension.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `ReferenceType.sourceDebugExtension()`

### canRequestVMDeathEvent

boolean canRequestVMDeathEvent()
Determines if the target VM supports the creation of `VMDeathRequest`s.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.4
See Also:
  - `EventRequestManager.createVMDeathRequest()`

### canGetMethodReturnValues

boolean canGetMethodReturnValues()
Determines if the target VM supports the inclusion of return values in `MethodExitEvent`s.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `EventRequestManager.createMethodExitRequest()`

### canGetInstanceInfo

boolean canGetInstanceInfo()
Determines if the target VM supports the accessing of class instances, instance counts, and referring objects.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `instanceCounts(List)`
  - `ReferenceType.instances(long)`
  - `ObjectReference.referringObjects(long)`

### canUseSourceNameFilters

boolean canUseSourceNameFilters()
Determines if the target VM supports the filtering of class prepare events by source name.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `ClassPrepareRequest.addSourceNameFilter(String)`

### canForceEarlyReturn

boolean canForceEarlyReturn()
Determines if the target VM supports the forcing of a method to return early.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `ThreadReference.forceEarlyReturn(Value)`

### canBeModified

boolean canBeModified()
Determines if the target VM is a read-only VM. If a method which would modify the state of the VM is called on a read-only VM, then `VMCannotBeModifiedException` is thrown.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.5

### canRequestMonitorEvents

boolean canRequestMonitorEvents()
Determines if the target VM supports the creation of `MonitorContendedEnterRequest`s. `MonitorContendedEnteredRequest`s. `MonitorWaitRequest`s. `MonitorWaitedRequest`s.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `EventRequestManager.createMonitorContendedEnterRequest()`
  - `EventRequestManager.createMonitorContendedEnteredRequest()`
  - `EventRequestManager.createMonitorWaitRequest()`
  - `EventRequestManager.createMonitorWaitedRequest()`

### canGetMonitorFrameInfo

boolean canGetMonitorFrameInfo()
Determines if the target VM supports getting which frame has acquired a monitor.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `ThreadReference.ownedMonitorsAndFrames()`

### canGetClassFileVersion

boolean canGetClassFileVersion()
Determines if the target VM supports reading class file major and minor versions.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `ReferenceType.majorVersion()`
  - `ReferenceType.minorVersion()`

### canGetConstantPool

boolean canGetConstantPool()
Determines if the target VM supports getting constant pool information of a class.

Returns:
  `true` if the feature is supported, `false` otherwise.
Since:
  1.6
See Also:
  - `ReferenceType.constantPoolCount()`
  - `ReferenceType.constantPool()`

### canGetModuleInfo

default boolean canGetModuleInfo()
Determines if the target VM supports getting information about modules.

Implementation Requirements:
  The default implementation returns `false`.
Returns:
  `true` if the feature is supported, `false` otherwise
Since:
  9
See Also:
  - `allModules()`
  - `ReferenceType.module()`
  - `ModuleReference`

### setDefaultStratum

void setDefaultStratum(String stratum)
Set this VM's default stratum (see `Location` for a discussion of strata). Overrides the per-class default set in the class file.

Affects location queries (such as, `Location.sourceName()`) and the line boundaries used in single stepping.

Parameters:
  `stratum` - the stratum to set as VM default, or null to use per-class defaults.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation.
Since:
  1.4

### getDefaultStratum

String getDefaultStratum()
Return this VM's default stratum.

Returns:
  `null` (meaning that the per-class default - `ReferenceType.defaultStratum()` - should be used) unless the default stratum has been set with `setDefaultStratum(String)`.
Since:
  1.4
See Also:
  - `setDefaultStratum(String)`
  - `ReferenceType.defaultStratum()`

### instanceCounts

long[] instanceCounts(List<? extends ReferenceType> refTypes)
Returns the number of instances of each ReferenceType in the 'refTypes' list. Only instances that are reachable for the purposes of garbage collection are counted.

Not all target virtual machines support this operation. Use `canGetInstanceInfo()` to determine if the operation is supported.

Parameters:
  `refTypes` - the list of `ReferenceType` objects for which counts are to be obtained.
Returns:
  an array of `long` containing one element for each element in the 'refTypes' list. Element i of the array contains the number of instances in the target VM of the ReferenceType at position i in the 'refTypes' list. If the 'refTypes' list is empty, a zero-length array is returned. If a ReferenceType in refTypes has been garbage collected, zero is returned for its instance count.
Throws:
  `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `canGetInstanceInfo()`
  `NullPointerException` - if the 'refTypes' list is null.
Since:
  1.6
See Also:
  - `ReferenceType.instances(long)`
  - `ObjectReference.referringObjects(long)`

### description

String description()
Returns text information on the target VM and the debugger support that mirrors it. No specific format for this information is guaranteed. Typically, this string contains version information for the target VM and debugger interfaces. More precise information on VM and JDI versions is available through `version()`, `VirtualMachineManager.majorInterfaceVersion()`, and `VirtualMachineManager.minorInterfaceVersion()`

Returns:
  the description.

### version

String version()
Returns the version of the Java Runtime Environment in the target VM as reported by the property `java.version`. For obtaining the JDI interface version, use `VirtualMachineManager.majorInterfaceVersion()` and `VirtualMachineManager.minorInterfaceVersion()`

Returns:
  the target VM version.

### name

String name()
Returns the name of the target VM as reported by the property `java.vm.name`.

Returns:
  the target VM name.

### setDebugTraceMode

void setDebugTraceMode(int traceFlags)
Traces the activities performed by the com.sun.jdi implementation. All trace information is output to System.err. The given trace flags are used to limit the output to only the information desired. The given flags are in effect and the corresponding trace will continue until the next call to this method.

Output is implementation dependent and trace mode may be ignored.

Parameters:
  `traceFlags` - identifies which kinds of tracing to enable.