ThreadReference (Java Debug Interface)

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## com.sun.jdi
Interface ThreadReference

All Superinterfaces:
  Mirror, ObjectReference, Value

public interface ThreadReference
extends ObjectReference

A thread object from the target VM. A ThreadReference is an `ObjectReference` with additional access to thread-specific information from the target VM.

Since:
  1.3

Field Summary
`static int` | `THREAD_STATUS_MONITOR` Thread is waiting on a java monitor
`static int` | `THREAD_STATUS_NOT_STARTED` Thread has not yet been started
`static int` | `THREAD_STATUS_RUNNING` Thread is runnable
`static int` | `THREAD_STATUS_SLEEPING` Thread is sleeping - Thread.sleep() or JVM_Sleep() was called
`static int` | `THREAD_STATUS_UNKNOWN` Thread status is unknown
`static int` | `THREAD_STATUS_WAIT` Thread is waiting - Thread.wait() or JVM_MonitorWait() was called
`static int` | `THREAD_STATUS_ZOMBIE` Thread has completed execution

Fields inherited from interface com.sun.jdi.ObjectReference
`INVOKE_NONVIRTUAL, INVOKE_SINGLE_THREADED`

Method Summary
`ObjectReference` | `currentContendedMonitor()` Returns an `ObjectReference` for the monitor, if any, for which this thread is currently waiting.
`StackFrame` | `frame(int index)` Returns the `StackFrame` at the given index in the thread's current call stack.
`int` | `frameCount()` Returns the number of stack frames in the thread's current call stack.
`List` | `frames()` Returns a List containing each `StackFrame` in the thread's current call stack.
`List` | `frames(int start, int length)` Returns a List containing a range of `StackFrame` mirrors from the thread's current call stack.
`void` | `interrupt()` Interrupts this thread.
`boolean` | `isAtBreakpoint()` Determines whether the thread is suspended at a breakpoint.
`boolean` | `isSuspended()` Determines whether the thread has been suspended by the the debugger.
`String` | `name()` Returns the name of this thread.
`List` | `ownedMonitors()` Returns a List containing an `ObjectReference` for each monitor owned by the thread.
`void` | `popFrames(StackFrame frame)` Pop stack frames.
`void` | `resume()` Resumes this thread.
`int` | `status()` Returns the thread's status.
`void` | `stop(ObjectReference throwable)` Stops this thread with an asynchronous exception.
`void` | `suspend()` Suspends this thread.
`int` | `suspendCount()` Returns the number of pending suspends for this thread.
`ThreadGroupReference` | `threadGroup()` Returns this thread's thread group.

Methods inherited from interface com.sun.jdi.ObjectReference
`disableCollection, enableCollection, entryCount, equals, getValue, getValues, hashCode, invokeMethod, isCollected, owningThread, referenceType, setValue, uniqueID, waitingThreads`

Methods inherited from interface com.sun.jdi.Value
`type`

Methods inherited from interface com.sun.jdi.Mirror
`toString, virtualMachine`

Field Detail

### THREAD_STATUS_UNKNOWN

    public static final int THREAD_STATUS_UNKNOWN

  Thread status is unknown

  See Also:
    Constant Field Values

### THREAD_STATUS_ZOMBIE

    public static final int THREAD_STATUS_ZOMBIE

  Thread has completed execution

  See Also:
    Constant Field Values

### THREAD_STATUS_RUNNING

    public static final int THREAD_STATUS_RUNNING

  Thread is runnable

  See Also:
    Constant Field Values

### THREAD_STATUS_SLEEPING

    public static final int THREAD_STATUS_SLEEPING

  Thread is sleeping - Thread.sleep() or JVM_Sleep() was called

  See Also:
    Constant Field Values

### THREAD_STATUS_MONITOR

    public static final int THREAD_STATUS_MONITOR

  Thread is waiting on a java monitor

  See Also:
    Constant Field Values

### THREAD_STATUS_WAIT

    public static final int THREAD_STATUS_WAIT

  Thread is waiting - Thread.wait() or JVM_MonitorWait() was called

  See Also:
    Constant Field Values

### THREAD_STATUS_NOT_STARTED

    public static final int THREAD_STATUS_NOT_STARTED

  Thread has not yet been started

  See Also:
    Constant Field Values

Method Detail

### name

    public String name()

  Returns the name of this thread.

  Returns:
    the string containing the thread name.

### suspend

    public void suspend()

  Suspends this thread. The thread can be resumed through `resume()` or resumed with other threads through `VirtualMachine.resume()`.

  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 `resume()`) the same number of times it has been suspended.

  Suspending single threads with this method has the same dangers as `Thread.suspend()`. If the suspended thread holds a monitor needed by another running thread, deadlock is possible in the target VM (at least until the suspended thread is resumed again).

  The suspended thread is guaranteed to remain suspended until resumed through one of the JDI resume methods mentioned above; the application in the target VM cannot resume the suspended thread through `Thread.resume()`.

### resume

    public void resume()

  Resumes this thread. If this thread was not previously suspended through `suspend()` or through `VirtualMachine.suspend()`, invoking this method has no effect. Otherwise, the count of pending suspends on this thread is decremented. If it is decremented to 0, the thread will continue to execute.

### suspendCount

    public int suspendCount()

  Returns the number of pending suspends for this thread. See `suspend()` for an explanation of counted suspends.

  Returns:
    pending suspend count as an integer

### stop

    public void stop(ObjectReference throwable)
              throws InvalidTypeException

  Stops this thread with an asynchronous exception. A debugger thread in the target VM will stop this thread with the given `Throwable` object.

  Parameters:
    `throwable` - the asynchronous exception to throw.
  Throws:
    `InvalidTypeException` - if `throwable` is not an instance of java.lang.Throwable in the target VM.
  See Also:
    `Thread.stop(Throwable)`

### interrupt

    public void interrupt()

  Interrupts this thread.

  See Also:
    `Thread.interrupt()`

### status

    public int status()

  Returns the thread's status. If the thread is not suspended the thread's current status is returned. If the thread is suspended, the thread's status before the suspension is returned (or `THREAD_STATUS_UNKNOWN` if this information is not available. `isSuspended()` can be used to determine if the thread has been suspended.

  Returns:
    one of `THREAD_STATUS_UNKNOWN`, `THREAD_STATUS_ZOMBIE`, `THREAD_STATUS_RUNNING`, `THREAD_STATUS_SLEEPING`, `THREAD_STATUS_MONITOR`, `THREAD_STATUS_WAIT`, `THREAD_STATUS_NOT_STARTED`,

### isSuspended

    public boolean isSuspended()

  Determines whether the thread has been suspended by the the debugger.

  Returns:
    `true` if the thread is currently suspended; `false` otherwise.

### isAtBreakpoint

    public boolean isAtBreakpoint()

  Determines whether the thread is suspended at a breakpoint.

  Returns:
    `true` if the thread is currently stopped at a breakpoint; `false` otherwise.

### threadGroup

    public ThreadGroupReference threadGroup()

  Returns this thread's thread group.

  Returns:
    a `ThreadGroupReference` that mirrors this thread's thread group in the target VM.

### frameCount

    public int frameCount()
                   throws IncompatibleThreadStateException

  Returns the number of stack frames in the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.

  Returns:
    an integer frame count
  Throws:
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM

### frames

    public List frames()
                throws IncompatibleThreadStateException

  Returns a List containing each `StackFrame` in the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.

  Returns:
    a List of `StackFrame` with the current frame first followed by each caller's frame.
  Throws:
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM

### frame

    public StackFrame frame(int index)
                     throws IncompatibleThreadStateException

  Returns the `StackFrame` at the given index in the thread's current call stack. Index 0 retrieves the current frame; higher indices retrieve caller frames. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.

  Parameters:
    `index` - the desired frame
  Returns:
    the requested `StackFrame`
  Throws:
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM
    `IndexOutOfBoundsException` - if the index is greater than or equal to `frameCount()` or is negative.

### frames

    public List frames(int start,
                       int length)
                throws IncompatibleThreadStateException

  Returns a List containing a range of `StackFrame` mirrors from the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.

  Parameters:
    `start` - the index of the first frame to retrieve. Index 0 represents the current frame.
    `length` - the number of frames to retrieve
  Returns:
    a List of `StackFrame` with the current frame first followed by each caller's frame.
  Throws:
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM
    `IndexOutOfBoundsException` - if the specified range is not within the range of stack frame indicies. That is, the exception is thrown if any of the following are true:

            start < 0
            start >= frameCount()
            length < 0
            (start+length) > frameCount()

### ownedMonitors

    public List ownedMonitors()
                       throws IncompatibleThreadStateException

  Returns a List containing an `ObjectReference` for each monitor owned by the thread. A monitor is owned by a thread if it has been entered (via the synchronized statement or entry into a synchronized method) and has not been relinquished through `Object.wait(long)`.

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

  Returns:
    a List of `ObjectReference` objects. The list has zero length if no monitors are owned by this thread.
  Throws:
    `UnsupportedOperationException` - if the target virtual machine does not support this operation.
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM

### currentContendedMonitor

    public ObjectReference currentContendedMonitor()
                                            throws IncompatibleThreadStateException

  Returns an `ObjectReference` for the monitor, if any, for which this thread is currently waiting. The thread can be waiting for a monitor through entry into a synchronized method, the synchronized statement, or `Object.wait(long)`. The `status()` method can be used to differentiate between the first two cases and the third.

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

  Returns:
    the `ObjectReference` corresponding to the contended monitor, or null if it is not waiting for a monitor.
  Throws:
    `UnsupportedOperationException` - if the target virtual machine does not support this operation.
    `IncompatibleThreadStateException` - if the thread is not suspended in the target VM

### popFrames

    public void popFrames(StackFrame frame)
                   throws IncompatibleThreadStateException

  Pop stack frames.

  All frames up to and including the `frame are popped off the stack. The frame previous to the parameter `frame will become the current frame.``

  After this operation, this thread will be suspended at the invoke instruction of the target method that created `frame`. The `frame`'s method can be reentered with a step into the instruction.

  The operand stack is restored, however, any changes to the arguments that occurred in the called method, remain. For example, if the method `foo`:

          void foo(int x) {
              System.out.println("Foo: " + x);
              x = 4;
              System.out.println("pop here");
          }

  was called with `foo(7)` and `foo` is popped at the second `println` and resumed, it will print: `Foo: 4`.

  Locks acquired by a popped frame are released when it is popped. This applies to synchronized methods that are popped, and to any synchronized blocks within them.

  Finally blocks are not executed.

  No aspect of state, other than this thread's execution point and locks, is affected by this call. Specifically, the values of fields are unchanged, as are external resources such as I/O streams. Additionally, the target program might be placed in a state that is impossible with normal program flow; for example, order of lock acquisition might be perturbed. Thus the target program may proceed differently than the user would expect.

  The specified thread must be suspended.

  All `StackFrame` objects for this thread are invalidated.

  No events are generated by this method.

  None of the frames through and including frame may be native.

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

  Parameters:
    `frame` - Stack frame to pop. `frame` is on this thread's call stack.
  Throws:
    `UnsupportedOperationException` - if the target virtual machine does not support this operation - see `VirtualMachine.canPopFrames()`.
    `IncompatibleThreadStateException` - if this thread is not suspended.
    `IllegalArgumentException` - if `frame` is not on this thread's call stack.
    `NativeMethodException` - if one of the frames that would be popped is that of a native method or if frame is native.
    `InvalidStackFrameException` - if `frame` has become invalid. Once this thread is resumed, the stack frame is no longer valid.
  Since:
    1.4

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Java Debug Interface

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