Knowning the coordinate of the starting point on a road ，it is need to calculate the coordinate of the intersection point that is between the road and the designated distance from the starting point。This kind of question just like the SDO-LRS.LOCATE_PT function in oracle spatial 。Does have the similiar API on GeoTools or neo4j spatial?
I'm not sure if geotools provides exactly this function. However, there is a related one in JTS, which both Geotools and Neo4j-Spatial use. Look at the JTS package com.vividsolutions.linearref, which has classes for searching along linear geometries for points, or creation/projection of points. I think the method LengthIndexedLine.extractPoint(length) might be what you are looking for.
In Neo4j-Spatial we have a utility which makes use of the LocationIndexedLine (but not yet LengthIndexedLine). See the test code in TestSpatialUtils, and the code it calls in SpatialTopologyUtils.
There are also two Google Summer of Code projects this year that are working on features related to this. One is specifically about Geoprocessing, and we will expose these kinds of functions with a simple API in Neo4j-Spatial. The other is more about data mining of OSM data models, but could also touch on these functions. For more information, watch the neo4j and udig mailing lists. By the end of the summer we will have a much richer set of Geoprocessing functions available in Neo4j-Spatial.