get the singleton instance of this class . concode_field_sep IUndoableOperation operationInProgress concode_elem_sep WorkspaceUndoMonitor instance concode_elem_sep String DEBUG_PREFIX concode_elem_sep IOperationHistoryListener historyListener concode_elem_sep int CHANGE_THRESHHOLD concode_elem_sep IResourceChangeListener resourceListener concode_elem_sep int numChanges concode_field_sep IOperationHistoryListener getOperationHistoryListener concode_elem_sep IOperationHistory getOperationHistory concode_elem_sep void flushWorkspaceHistory concode_elem_sep void resetChangeCount concode_elem_sep IResourceChangeListener getResourceChangeListener concode_elem_sep void incrementChangeCount concode_elem_sep void shutdown concode_elem_sep void checkOperationHistory
WorkspaceUndoMonitor function ( ) { if ( instance == null ) { instance = new WorkspaceUndoMonitor ( ) ; } return instance ; }