Bug 211839 String grouping unit type needs to support interval range.
Build ID: I20071101-2000 As Chart has supported, the String grouping unit type can be set interval range, the interval range means that the string group will base on row count distinction. For instance, let's say we have a,b,c,d,e,f,g , and set interval range to 2, the grouping result should be a,c,e,g. Now it is a requirement that DtE support the grouping type.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/executor/transform/group/GroupCalculationUtil.java
try
				{
					comp1 = (Comparable) DataTypeUtil.toDouble( obj1 );
					comp2 = (Comparable) DataTypeUtil.toDouble( obj2 );
				}
				catch ( BirtException ex )
				{
					
				}
			}
			return comp1.compareTo( comp2 );
		}
		else
		{
			return obj1.toString( ).compareTo( obj2.toString( ) );
		}
	}
}
/**
 * A creator class implemented ICachedObjectCreator. This class is used to
 * create GroupBoundaryInfo object.
 * 
 * @author Administrator
 * 
 */
class GroupBoundaryInfoCreator implements ICachedObjectCreator
{
	/*
	 * (non-Javadoc)
	 * @see org.eclipse.birt.data.engine.cache.ICachedObjectCreator#createInstance(java.lang.Object[])