Package org.eclipse.core.runtime

Class SubMonitor

java.lang.Object
org.eclipse.core.runtime.SubMonitor
All Implemented Interfaces:
IProgressMonitor, IProgressMonitorWithBlocking
public final class SubMonitor extends Object implements IProgressMonitorWithBlocking

A progress monitor that uses a given amount of work ticks from a parent monitor. This is intended as a safer, easier-to-use alternative to SubProgressMonitor. The main benefits of SubMonitor over SubProgressMonitor are:

  • It is not necessary to call beginTask() or done() on an instance of SubMonitor.
  • SubMonitor has a simpler syntax for creating nested monitors.
  • SubMonitor is more efficient for deep recursion chains.
  • SubMonitor has a setWorkRemaining method that allows the remaining space on the monitor to be redistributed without reporting any work.
  • SubMonitor protects the caller from common progress reporting bugs in a called method. For example, if a called method fails to call done() on the given monitor or fails to consume all the ticks on the given monitor, the parent will correct the problem after the method returns.

USAGE:

When implementing a method that accepts an IProgressMonitor:

  • At the start of your method, use SubMonitor.convert(...). to convert the IProgressMonitor into a SubMonitor.
  • Use SubMonitor.split(...) whenever you need to call another method that accepts an IProgressMonitor.

Example: Recommended usage

This example demonstrates how the recommended usage of SubMonitor makes it unnecessary to call IProgressMonitor.done() in most situations.

It is never necessary to call done() on a monitor obtained from convert or progress.split(). In this example, there is no guarantee that monitor is an instance of SubMonitor, making it necessary to call monitor.done(). The JavaDoc contract makes this the responsibility of the caller. 

      // @param monitor the progress monitor to use for reporting progress to the user. It is the caller's responsibility
      //        to call done() on the given monitor. Accepts null, indicating that no progress should be
      //        reported and that the operation cannot be cancelled.
      //
      void doSomething(IProgressMonitor monitor) {
          // Convert the given monitor into a progress instance 
          SubMonitor progress = SubMonitor.convert(monitor, 100);
              
          // Use 30% of the progress to do some work
          doSomeWork(progress.split(30));
          
          // Advance the monitor by another 30%
          progress.split(30);
          
          // Use the remaining 40% of the progress to do some more work
          doSomeWork(progress.split(40)); 
      }

Example: Branches

This example demonstrates how to smoothly report progress in situations where some of the work is optional. 

 void doSomething(IProgressMonitor monitor) {
        SubMonitor progress = SubMonitor.convert(monitor, 100);
 
        if (condition) {
                // Use 50% of the progress to do some work
                doSomeWork(progress.split(50));
        }
 
        // Don't report any work, but ensure that we have 50 ticks remaining on the
        // progress monitor.
        // If we already consumed 50 ticks in the above branch, this is a no-op.
        // Otherwise, the remaining
        // space in the monitor is redistributed into 50 ticks.
 
        progress.setWorkRemaining(50);
 
        // Use the remainder of the progress monitor to do the rest of the work
        doSomeWork(progress.split(50));
 }

Please beware of the following anti-pattern: 

 if (condition) {
        // Use 50% of the progress to do some work
        doSomeWork(progress.split(50));
 } else {
        // Bad: Causes the progress monitor to appear to start at 50%, wasting half
        // of the
        // space in the monitor.
        progress.worked(50);
 }

Example: Loops

This example demonstrates how to report progress in a loop. 

 void doSomething(IProgressMonitor monitor, Collection someCollection) {
        SubMonitor progress = SubMonitor.convert(monitor, 100);

        // Create a new progress monitor that uses 70% of the total progress and will
        // allocate one tick
        // for each element of the given collection.
        SubMonitor loopProgress = progress.split(70).setWorkRemaining(someCollection.size());
 
        for (Iterator iter = someCollection.iterator(); iter.hasNext();) {
                Object next = iter.next();
 
                doWorkOnElement(next, loopProgress.split(1));
        }
 
        // Use the remaining 30% of the progress monitor to do some work outside the
        // loop
        doSomeWork(progress.split(30));
 }

Example: Infinite progress

This example demonstrates how to report logarithmic progress in situations where the number of ticks cannot be easily computed in advance. 

 void doSomething(IProgressMonitor monitor, LinkedListNode node) {
        SubMonitor progress = SubMonitor.convert(monitor);
 
        while (node != null) {
                // Regardless of the amount of progress reported so far,
                // use 0.01% of the space remaining in the monitor to process the next node.
                progress.setWorkRemaining(10000);
 
                doWorkOnElement(node, progress.split(1));
 
                node = node.next;
        }
 }

This class can be used without OSGi running.

Since:
org.eclipse.equinox.common 3.3

  • Field Details

    • SUPPRESS_SUBTASK

      public static final int SUPPRESS_SUBTASK
      May be passed as a flag to split(int). Indicates that the calls to subTask on the child should be ignored. Without this flag, calling subTask on the child will result in a call to subTask on its parent.
      See Also:

    • SUPPRESS_BEGINTASK

      public static final int SUPPRESS_BEGINTASK
      May be passed as a flag to split(int). Indicates that strings passed into beginTask should be ignored. If this flag is specified, then the progress monitor instance will accept null as the first argument to beginTask. Without this flag, any string passed to beginTask will result in a call to setTaskName on the parent.
      See Also:

    • SUPPRESS_SETTASKNAME

      public static final int SUPPRESS_SETTASKNAME
      May be passed as a flag to split(int). Indicates that strings passed into setTaskName should be ignored. If this string is omitted, then a call to setTaskName on the child will result in a call to setTaskName on the parent.
      See Also:

    • SUPPRESS_ISCANCELED

      public static final int SUPPRESS_ISCANCELED
      May be passed as a flag to split(int). Indicates that isCanceled should always return false.
      Since:
      3.8
      See Also:

    • SUPPRESS_ALL_LABELS

      public static final int SUPPRESS_ALL_LABELS
      May be passed as a flag to split(int). Indicates that strings passed to setTaskName, subTask, and beginTask should all be ignored.
      See Also:

    • SUPPRESS_NONE

      public static final int SUPPRESS_NONE
      May be passed as a flag to split(int). Indicates that strings passed to setTaskName, subTask, and beginTask should all be propagated to the parent.
      See Also:

  • Method Details

    • convert

      public static SubMonitor convert(IProgressMonitor monitor)

      Converts an unknown (possibly null) IProgressMonitor into a SubMonitor. It is not necessary to call done() on the result, but the caller is responsible for calling done() on the argument. Calls beginTask on the argument.

      This method should generally be called at the beginning of a method that accepts an IProgressMonitor in order to convert the IProgressMonitor into a SubMonitor.

      Since it is illegal to call beginTask on the same IProgressMonitor more than once, the same instance of IProgressMonitor must not be passed to convert more than once.

      Parameters:
      monitor - monitor to convert to a SubMonitor instance or null. Treats null as a new instance of NullProgressMonitor.
      Returns:
      a SubMonitor instance that adapts the argument

    • convert

      public static SubMonitor convert(IProgressMonitor monitor, int work)

      Converts an unknown (possibly null) IProgressMonitor into a SubMonitor allocated with the given number of ticks. It is not necessary to call done() on the result, but the caller is responsible for calling done() on the argument. Calls beginTask on the argument.

      This method should generally be called at the beginning of a method that accepts an IProgressMonitor in order to convert the IProgressMonitor into a SubMonitor.

      Since it is illegal to call beginTask on the same IProgressMonitor more than once, the same instance of IProgressMonitor must not be passed to convert more than once.

      Parameters:
      monitor - monitor to convert to a SubMonitor instance or null. Treats null as a new instance of NullProgressMonitor.
      work - number of ticks that will be available in the resulting monitor
      Returns:
      a SubMonitor instance that adapts the argument

    • convert

      public static SubMonitor convert(IProgressMonitor monitor, String taskName, int work)

      Converts an unknown (possibly null) IProgressMonitor into a SubMonitor allocated with the given number of ticks. It is not necessary to call done() on the result, but the caller is responsible for calling done() on the argument. Calls beginTask on the argument.

      This method should generally be called at the beginning of a method that accepts an IProgressMonitor in order to convert the IProgressMonitor into a SubMonitor.

      Since it is illegal to call beginTask on the same IProgressMonitor more than once, the same instance of IProgressMonitor must not be passed to convert more than once.

      Parameters:
      monitor - to convert into a SubMonitor instance or null. If given a null argument, the resulting SubMonitor will not report its progress anywhere.
      taskName - user readable name to pass to monitor.beginTask. Never null.
      work - initial number of ticks to allocate for children of the SubMonitor
      Returns:
      a new SubMonitor instance that is a child of the given monitor

    • done

      public static void done(IProgressMonitor monitor)
      Calls done() on the given monitor if is non-null. If the given monitor is null, this is a no-op.

      This is a convenience method intended to reduce the boilerplate around code which must call done() on a possibly-null monitor.

      Parameters:
      monitor - a progress monitor or null
      Since:
      3.8

    • setWorkRemaining

      public SubMonitor setWorkRemaining(int workRemaining)

      Sets the work remaining for this SubMonitor instance. This is the total number of ticks that may be reported by all subsequent calls to worked(int), split(int), etc. This may be called many times for the same SubMonitor instance. When this method is called, the remaining space on the progress monitor is redistributed into the given number of ticks.

      It doesn't matter how much progress has already been reported with this SubMonitor instance. If you call setWorkRemaining(100), you will be able to report 100 more ticks of work before the progress meter reaches 100%.

      Parameters:
      workRemaining - total number of remaining ticks
      Returns:
      the receiver

    • isCanceled

      public boolean isCanceled()
      Description copied from interface: IProgressMonitor
      Returns whether cancelation of current operation has been requested. Long-running operations should poll to see if cancelation has been requested.
      Specified by:
      isCanceled in interface IProgressMonitor
      Returns:
      true if cancellation has been requested, and false otherwise
      See Also:

    • checkCanceled

      public SubMonitor checkCanceled() throws OperationCanceledException
      Checks whether cancellation of current operation has been requested and throws an OperationCanceledException if it was the case. This method is a shorthand for: 
       if (monitor.isCanceled())
        throw new OperationCanceledException();
      Returns:
      this SubMonitor to allow for chained invocation
      Throws:
      OperationCanceledException - if cancellation has been requested
      Since:
      3.9
      See Also:

    • setTaskName

      public void setTaskName(String name)
      Description copied from interface: IProgressMonitor
      Sets the task name to the given value. This method is used to restore the task label after a nested operation was executed. Normally there is no need for clients to call this method.
      Specified by:
      setTaskName in interface IProgressMonitor
      Parameters:
      name - the name (or description) of the main task
      See Also:

    • beginTask

      public void beginTask(String name, int totalWork)
      Starts a new main task. The string argument is ignored if and only if the SUPPRESS_BEGINTASK flag has been set on this SubMonitor instance.

      This method is equivalent calling setWorkRemaining(...) on the receiver. Unless the SUPPRESS_BEGINTASK flag is set, this will also be equivalent to calling setTaskName(...) on the parent.

      Specified by:
      beginTask in interface IProgressMonitor
      Parameters:
      name - new main task name
      totalWork - number of ticks to allocate
      See Also:

    • done

      public void done()
      Description copied from interface: IProgressMonitor
      Notifies that the work is done; that is, either the main task is completed or the user canceled it. This method may be called more than once (implementations should be prepared to handle this case).
      Specified by:
      done in interface IProgressMonitor

    • internalWorked

      public void internalWorked(double work)
      Description copied from interface: IProgressMonitor
      Internal method to handle scaling correctly. This method must not be called by a client. Clients should always use the method worked(int).
      Specified by:
      internalWorked in interface IProgressMonitor
      Parameters:
      work - the amount of work done

    • subTask

      public void subTask(String name)
      Description copied from interface: IProgressMonitor
      Notifies that a subtask of the main task is beginning. Subtasks are optional; the main task might not have subtasks.
      Specified by:
      subTask in interface IProgressMonitor
      Parameters:
      name - the name (or description) of the subtask

    • worked

      public void worked(int work)
      Description copied from interface: IProgressMonitor
      Notifies that a given number of work unit of the main task has been completed. Note that this amount represents an installment, as opposed to a cumulative amount of work done to date.
      Specified by:
      worked in interface IProgressMonitor
      Parameters:
      work - a non-negative number of work units just completed

    • setCanceled

      public void setCanceled(boolean b)
      Description copied from interface: IProgressMonitor
      Sets the cancel state to the given value.
      Specified by:
      setCanceled in interface IProgressMonitor
      Parameters:
      b - true indicates that cancelation has been requested (but not necessarily acknowledged); false clears this flag
      See Also:

    • newChild

      public SubMonitor newChild(int totalWork)

      Creates a new SubMonitor that will consume the given number of ticks from its parent. Shorthand for calling newChild(int, int) with (totalWork, SUPPRESS_BEGINTASK).

      This is much like split(int) but it does not check for cancellation and will not throw OperationCanceledException. New code should consider using split(int) to benefit from automatic cancellation checks.

      Parameters:
      totalWork - number of ticks to consume from the receiver
      Returns:
      new sub progress monitor that may be used in place of a new SubMonitor

    • newChild

      public SubMonitor newChild(int totalWork, int suppressFlags)

      This is much like split(int), but it does not check for cancellation and will not throw OperationCanceledException. New code should consider using split(int) to benefit from automatic cancellation checks.

      Creates a sub progress monitor that will consume the given number of ticks from the receiver. It is not necessary to call beginTask or done on the result. However, the resulting progress monitor will not report any work after the first call to done() or before ticks are allocated. Ticks may be allocated by calling beginTask or setWorkRemaining.

      Each SubMonitor only has one active child at a time. Each time newChild() is called, the result becomes the new active child and any unused progress from the previously-active child is consumed.

      This is property makes it unnecessary to call done() on a SubMonitor instance, since child monitors are automatically cleaned up the next time the parent is touched. 

        
      ////////////////////////////////////////////////////////////////////////////
      // Example 1: Typical usage of newChild
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100); 
          doSomething(progress.newChild(50));
          doSomethingElse(progress.newChild(50));
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 2: Demonstrates the function of active children. Creating children
      // is sufficient to smoothly report progress, even if worked(...) and done()
      // are never called.
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          for (int i = 0; i < 100; i++) {
              // Creating the next child monitor will clean up the previous one,
              // causing progress to be reported smoothly even if we don't do anything
              // with the monitors we create
                progress.newChild(1);
          }
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 3: Demonstrates a common anti-pattern
      void wrongMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // WRONG WAY: Won't have the intended effect, as only one of these progress
          // monitors may be active at a time and the other will report no progress.
          callMethod(progress.newChild(50), computeValue(progress.newChild(50)));
      }
      
      void rightMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // RIGHT WAY: Break up method calls so that only one SubMonitor is in use at a time.
          Object someValue = computeValue(progress.newChild(50));
          callMethod(progress.newChild(50), someValue);
      }
      Parameters:
      totalWork - number of ticks to consume from the receiver
      suppressFlags - a bitwise combination of SUPPRESS_* flags. They can be used to suppress various behaviors on the newly-created monitor. Callers should generally include the SUPPRESS_BEGINTASK flag unless they are invoking a method whose JavaDoc specifically states that the string argument to beginTask(String, int) must be preserved.
      Returns:
      new sub progress monitor that may be used in place of a new SubMonitor

    • split

      public SubMonitor split(int totalWork) throws OperationCanceledException
      This is shorthand for calling split(totalWork, SUPPRESS_BEGINTASK). See split(int, int) for more details.

      Creates a sub progress monitor that will consume the given number of ticks from the receiver. It is not necessary to call beginTask or done on the result. However, the resulting progress monitor will not report any work after the first call to done() or before ticks are allocated. Ticks may be allocated by calling beginTask(java.lang.String, int) or setWorkRemaining(int).

      This method is much like newChild(int), but it will additionally check for cancellation and will throw an OperationCanceledException if the monitor has been cancelled. Not every call to this method will trigger a cancellation check. The checks will be performed as often as possible without degrading the performance of the caller.

      Each SubMonitor only has one active child at a time. Each time newChild(int) or split(int) is called, the result becomes the new active child and any unused progress from the previously-active child is consumed.

      This makes it unnecessary to call done() on a SubMonitor instance, since child monitors are automatically cleaned up the next time the parent is touched. 

       
      ////////////////////////////////////////////////////////////////////////////
      // Example 1: Typical usage of split
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100); 
          doSomething(progress.split(50));
          doSomethingElse(progress.split(50));
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 2: Demonstrates the function of active children. Creating children
      // is sufficient to smoothly report progress, even if worked(...) and done()
      // are never called.
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          for (int i = 0; i < 100; i++) {
              // Creating the next child monitor will clean up the previous one,
              // causing progress to be reported smoothly even if we don't do anything
              // with the monitors we create
                progress.split(1);
          }
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 3: Demonstrates a common anti-pattern
      void wrongMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // WRONG WAY: Won't have the intended effect, as only one of these progress
          // monitors may be active at a time and the other will report no progress.
          callMethod(progress.split(50), computeValue(progress.split(50)));
      }
      
      void rightMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // RIGHT WAY: Break up method calls so that only one SubMonitor is in use at a time.
          Object someValue = computeValue(progress.split(50));
          callMethod(progress.split(50), someValue);
      }
      Parameters:
      totalWork - number of ticks to consume from the receiver
      Returns:
      a new SubMonitor instance
      Throws:
      OperationCanceledException - if the monitor has been cancelled
      Since:
      3.8

    • split

      public SubMonitor split(int totalWork, int suppressFlags) throws OperationCanceledException

      Creates a sub progress monitor that will consume the given number of ticks from the receiver. It is not necessary to call beginTask or done on the result. However, the resulting progress monitor will not report any work after the first call to done() or before ticks are allocated. Ticks may be allocated by calling beginTask(java.lang.String, int) or setWorkRemaining(int)

      This method is much like newChild(int), but will additionally check for cancellation and will throw an OperationCanceledException if the monitor has been cancelled. Not every call to this method will trigger a cancellation check. The checks will be performed as often as possible without degrading the performance of the caller.

      Each SubMonitor only has one active child at a time. Each time newChild(int) or split(int) is called, the result becomes the new active child and any unused progress from the previously-active child is consumed.

      This is property makes it unnecessary to call done() on a SubMonitor instance, since child monitors are automatically cleaned up the next time the parent is touched. 

        
      ////////////////////////////////////////////////////////////////////////////
      // Example 1: Typical usage of split
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100); 
          doSomething(progress.split(50));
          doSomethingElse(progress.split(50));
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 2: Demonstrates the function of active children. Creating children
      // is sufficient to smoothly report progress, even if worked(...) and done()
      // are never called.
      void myMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          for (int i = 0; i < 100; i++) {
              // Creating the next child monitor will clean up the previous one,
              // causing progress to be reported smoothly even if we don't do anything
              // with the monitors we create
                progress.split(1);
          }
      }
      
      ////////////////////////////////////////////////////////////////////////////
      // Example 3: Demonstrates a common anti-pattern
      void wrongMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // WRONG WAY: Won't have the intended effect, as only one of these progress
          // monitors may be active at a time and the other will report no progress.
          callMethod(progress.split(50), computeValue(progress.split(50)));
      }
      
      void rightMethod(IProgressMonitor parent) {
          SubMonitor progress = SubMonitor.convert(parent, 100);
          
          // RIGHT WAY: Break up method calls so that only one SubMonitor is in use at a time.
          Object someValue = computeValue(progress.split(50));
          callMethod(progress.split(50), someValue);
      }
      Parameters:
      totalWork - number of ticks to consume from the receiver
      suppressFlags - a bitwise combination of SUPPRESS_* flags. They can be used to suppress various behaviors on the newly-created monitor. Callers should generally include the SUPPRESS_BEGINTASK flag unless they are invoking a method whose JavaDoc specifically states that the string argument to beginTask(String, int) must be preserved.
      Returns:
      new sub progress monitor that may be used in place of a new SubMonitor
      Throws:
      OperationCanceledException - if the monitor has been cancelled
      Since:
      3.8

    • clearBlocked

      public void clearBlocked()
      Description copied from interface: IProgressMonitor
      Clears the blocked state of the running operation. If a running operation ever calls setBlocked, it must eventually call clearBlocked before the operation completes.
      Specified by:
      clearBlocked in interface IProgressMonitor
      See Also:

    • setBlocked

      public void setBlocked(IStatus reason)
      Description copied from interface: IProgressMonitor
      Indicates that this operation is blocked by some background activity. If a running operation ever calls setBlocked, it must eventually call clearBlocked before the operation completes.

      If the caller is blocked by a currently executing job, this method will return an IJobStatus indicating the job that is currently blocking the caller. If this blocking job is not known, this method will return a plain informational IStatus object.

      Specified by:
      setBlocked in interface IProgressMonitor
      Parameters:
      reason - an optional status object whose message describes the reason why this operation is blocked, or null if this information is not available.
      See Also:

    • eq

      protected static boolean eq(Object o1, Object o2)

    • toString

      public String toString()
      Overrides:
      toString in class Object