VirtualMachine (Java Debug Interface )
Keywords: com.sun.jdi.VirtualMachine interface
Date: 2017-01-22

com.sun.jdi

## Interface VirtualMachine

- All Superinterfaces:
    Mirror
  All Known Subinterfaces:
    PathSearchingVirtualMachine

      @Exported
      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 and Description
    --- | ---
    `static int` | `TRACE_ALL` All tracing is enabled.
    `static int` | `TRACE_EVENTS` Tracing enabled for internal event handling.
    `static int` | `TRACE_NONE` All tracing is disabled.
    `static int` | `TRACE_OBJREFS` Tracing enabled for internal management of object references.
    `static int` | `TRACE_RECEIVES` Tracing enabled for JDWP packets received from target VM.
    `static int` | `TRACE_REFTYPES` Tracing enabled for internal managment of reference types.
    `static int` | `TRACE_SENDS` Tracing enabled for JDWP packets sent to target VM.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `List<ReferenceType>` | `allClasses()` Returns all loaded types.
    `List<ThreadReference>` | `allThreads()` Returns a list of the currently running threads.
    `boolean` | `canAddMethod()` Determines if the target VM supports the addition of methods when performing class redefinition.
    `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.
    `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()` Determines if the target VM supports unrestricted changes when performing class redefinition.
    `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 inherited from interface com.sun.jdi.Mirror

      `toString, virtualMachine`

- - ### Field Detail

    - #### 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 managment 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 Detail

    - #### 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. For each loaded type in the target VM a `ReferenceType` will be placed in the returned list. The list will include ReferenceTypes which mirror classes, interfaces, and array types.

      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.

      Returns:
        a list of `ReferenceType` objects, each mirroring a loaded type in the target VM.

    - #### 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 indicies 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 following will throw this exception
          - changing the schema (the fields)
          - changing the hierarchy (subclasses, interfaces)
          - deleting a method
          - changing class modifiers
          - changing method modifiers
        `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(com.sun.jdi.StackFrame)`, `canRedefineClasses()`, `canAddMethod()`, `canUnrestrictedlyRedefineClasses()`

    - #### allThreads

          List<ThreadReference> allThreads()

      Returns a list of the currently running threads. For each running thread in the target VM, a `ThreadReference` that mirrors it is placed in the list. The returned list contains threads created through java.lang.Thread, all native threads attached to the target VM through JNI, and system threads created by the target VM. Thread objects that have not yet been started (see `Thread.start()`) and thread objects that have completed their execution are not included in the returned list.
      Returns:
        a list of `ThreadReference` objects, one for each running thread in the mirrored VM.

    - #### suspend

          void suspend()

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

      Unlike `Thread.suspend()`, 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 `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 `canBeModified()`.
      See Also:
        `suspend()`

    - #### 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(com.sun.jdi.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(com.sun.jdi.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(java.util.Map<? extends com.sun.jdi.ReferenceType, byte[]>)`

    - #### canAddMethod

          boolean canAddMethod()

      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(java.util.Map<? extends com.sun.jdi.ReferenceType, byte[]>)`

    - #### canUnrestrictedlyRedefineClasses

          boolean canUnrestrictedlyRedefineClasses()

      Determines if the target VM supports unrestricted changes when performing class redefinition.
      Returns:
        `true` if the feature is supported, `false` otherwise.
      Since:
        1.4
      See Also:
        `redefineClasses(java.util.Map<? extends com.sun.jdi.ReferenceType, byte[]>)`

    - #### 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(com.sun.jdi.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(java.util.List<? extends com.sun.jdi.ReferenceType>)`, `ReferenceType.instances(long)`, `ObjectReference.referringObjects(long)`

    - #### canUseSourceNameFilters

          boolean canUseSourceNameFilters()

      Determines if the target VM supports the filtering of class prepare events by source name. see `ClassPrepareRequest.addSourceNameFilter(java.lang.String)`.
      Returns:
        `true` if the feature is supported, `false` otherwise.
      Since:
        1.6

    - #### 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()`

    - #### 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.

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